diff --git a/backend/src/db/schema.sql b/backend/src/db/schema.sql
index e154c0a..faf9fc6 100644
--- a/backend/src/db/schema.sql
+++ b/backend/src/db/schema.sql
@@ -76,6 +76,63 @@ CREATE TABLE IF NOT EXISTS app_settings (
 -- Global admin flag (first user created via web installer)
 ALTER TABLE users ADD COLUMN IF NOT EXISTS is_admin BOOLEAN NOT NULL DEFAULT FALSE;
 
+-- Profile / appearance / locale settings (edited via settings window)
+ALTER TABLE users ADD COLUMN IF NOT EXISTS avatar TEXT NOT NULL DEFAULT '';
+ALTER TABLE users ADD COLUMN IF NOT EXISTS locale TEXT NOT NULL DEFAULT 'en';
+ALTER TABLE users ADD COLUMN IF NOT EXISTS theme TEXT NOT NULL DEFAULT 'system';
+ALTER TABLE users ADD COLUMN IF NOT EXISTS bg_image TEXT NOT NULL DEFAULT '';
+ALTER TABLE users ADD COLUMN IF NOT EXISTS bg_blur BOOLEAN NOT NULL DEFAULT TRUE;
+
+-- Books: independent containers that hold pages (collapsible in sidebar)
+CREATE TABLE IF NOT EXISTS books (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  workspace_id UUID NOT NULL REFERENCES workspaces(id) ON DELETE CASCADE,
+  title TEXT NOT NULL DEFAULT 'Untitled book' CHECK (char_length(title) BETWEEN 1 AND 200),
+  icon TEXT NOT NULL DEFAULT '📚',
+  position DOUBLE PRECISION NOT NULL DEFAULT 0,
+  created_by UUID REFERENCES users(id) ON DELETE SET NULL,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX IF NOT EXISTS idx_books_workspace ON books(workspace_id);
+
+-- Pages can optionally live inside a book (book_id NULL = top-level page)
+ALTER TABLE pages ADD COLUMN IF NOT EXISTS book_id UUID REFERENCES books(id) ON DELETE CASCADE;
+CREATE INDEX IF NOT EXISTS idx_pages_book ON pages(book_id);
+
+-- Tasks: can link to a book and/or a page, optional deadline (feeds the calendar)
+CREATE TABLE IF NOT EXISTS tasks (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  workspace_id UUID NOT NULL REFERENCES workspaces(id) ON DELETE CASCADE,
+  book_id UUID REFERENCES books(id) ON DELETE SET NULL,
+  page_id UUID REFERENCES pages(id) ON DELETE SET NULL,
+  title TEXT NOT NULL CHECK (char_length(title) BETWEEN 1 AND 300),
+  status TEXT NOT NULL DEFAULT 'todo' CHECK (status IN ('todo','doing','done')),
+  priority TEXT NOT NULL DEFAULT 'normal' CHECK (priority IN ('low','normal','high')),
+  due_at TIMESTAMPTZ NULL,
+  position DOUBLE PRECISION NOT NULL DEFAULT 0,
+  created_by UUID REFERENCES users(id) ON DELETE SET NULL,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX IF NOT EXISTS idx_tasks_workspace ON tasks(workspace_id);
+CREATE INDEX IF NOT EXISTS idx_tasks_due ON tasks(workspace_id, due_at);
+
+-- Time tracking entries (open entry = running timer, ended_at IS NULL)
+CREATE TABLE IF NOT EXISTS time_entries (
+  id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  workspace_id UUID NOT NULL REFERENCES workspaces(id) ON DELETE CASCADE,
+  user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  book_id UUID REFERENCES books(id) ON DELETE SET NULL,
+  page_id UUID REFERENCES pages(id) ON DELETE SET NULL,
+  description TEXT NOT NULL DEFAULT '',
+  started_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  ended_at TIMESTAMPTZ NULL,
+  duration_seconds INTEGER NULL,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX IF NOT EXISTS idx_time_ws_user ON time_entries(workspace_id, user_id);
+
 -- Ensure workspace owner is always a member with role=owner
 CREATE OR REPLACE FUNCTION ensure_owner_membership() RETURNS trigger AS $$
 BEGIN
@@ -110,3 +167,11 @@ FOR EACH ROW EXECUTE FUNCTION touch_updated_at();
 DROP TRIGGER IF EXISTS trg_pages_touch ON pages;
 CREATE TRIGGER trg_pages_touch BEFORE UPDATE ON pages
 FOR EACH ROW EXECUTE FUNCTION touch_updated_at();
+
+DROP TRIGGER IF EXISTS trg_books_touch ON books;
+CREATE TRIGGER trg_books_touch BEFORE UPDATE ON books
+FOR EACH ROW EXECUTE FUNCTION touch_updated_at();
+
+DROP TRIGGER IF EXISTS trg_tasks_touch ON tasks;
+CREATE TRIGGER trg_tasks_touch BEFORE UPDATE ON tasks
+FOR EACH ROW EXECUTE FUNCTION touch_updated_at();
diff --git a/backend/src/index.js b/backend/src/index.js
index 3c07d00..ec906d9 100644
--- a/backend/src/index.js
+++ b/backend/src/index.js
@@ -11,6 +11,10 @@ import setupRoutes, { isInstalled } from './routes/setup.js';
 import workspaceRoutes from './routes/workspaces.js';
 import pageRoutes from './routes/pages.js';
 import userRoutes from './routes/users.js';
+import bookRoutes from './routes/books.js';
+import taskRoutes from './routes/tasks.js';
+import timeRoutes from './routes/time.js';
+import adminRoutes from './routes/admin.js';
 import { initSocket } from './socket.js';
 
 const app = express();
@@ -43,6 +47,10 @@ app.use('/api/auth', rateLimit({ windowMs: 15 * 60 * 1000, max: 100 }), authRout
 app.use('/api/workspaces', workspaceRoutes);
 app.use('/api/pages', pageRoutes);
 app.use('/api/users', userRoutes);
+app.use('/api/books', bookRoutes);
+app.use('/api/tasks', taskRoutes);
+app.use('/api/time', timeRoutes);
+app.use('/api/admin', adminRoutes);
 
 app.get('/api/health', async (_req, res) => {
   try {
diff --git a/backend/src/routes/admin.js b/backend/src/routes/admin.js
new file mode 100644
index 0000000..a3abb4f
--- /dev/null
+++ b/backend/src/routes/admin.js
@@ -0,0 +1,62 @@
+import { Router } from 'express';
+import { query } from '../config/db.js';
+import { requireAuth } from '../middleware/auth.js';
+import { requireAdmin } from './guards.js';
+
+const router = Router();
+router.use(requireAuth, requireAdmin);
+
+// GET /api/admin/overview — counts + recent users
+router.get('/overview', async (_req, res) => {
+  const [[u], [w], [b], [p], [t], [e]] = await Promise.all(
+    ['users', 'workspaces', 'books', 'pages', 'tasks', 'time_entries'].map(
+      (tbl) => query(`SELECT COUNT(*)::int AS c FROM ${tbl}`).then((r) => r.rows),
+    ),
+  );
+  const { rows: recent } = await query(
+    'SELECT id, name, email, is_admin, created_at FROM users ORDER BY created_at DESC LIMIT 8',
+  );
+  return res.json({
+    counts: {
+      users: u.c, workspaces: w.c, books: b.c, pages: p.c, tasks: t.c, timeEntries: e.c,
+    },
+    recentUsers: recent,
+  });
+});
+
+// GET /api/admin/users
+router.get('/users', async (_req, res) => {
+  const { rows } = await query(
+    `SELECT u.id, u.name, u.email, u.is_admin, u.locale, u.created_at,
+       (SELECT COUNT(*)::int FROM workspace_members m WHERE m.user_id = u.id) AS workspaces
+     FROM users u ORDER BY u.created_at`,
+  );
+  return res.json({ users: rows });
+});
+
+// PATCH /api/admin/users/:id { is_admin }
+router.patch('/users/:id', async (req, res) => {
+  const { is_admin } = req.body ?? {};
+  if (typeof is_admin !== 'boolean') return res.status(400).json({ error: 'is_admin boolean required' });
+  if (req.params.id === req.user.id && is_admin === false) {
+    return res.status(400).json({ error: 'You cannot demote yourself' });
+  }
+  const { rows } = await query(
+    'UPDATE users SET is_admin = $1 WHERE id = $2 RETURNING id, name, email, is_admin',
+    [is_admin, req.params.id],
+  );
+  if (!rows[0]) return res.status(404).json({ error: 'User not found' });
+  return res.json({ user: rows[0] });
+});
+
+// DELETE /api/admin/users/:id
+router.delete('/users/:id', async (req, res) => {
+  if (req.params.id === req.user.id) {
+    return res.status(400).json({ error: 'You cannot delete yourself' });
+  }
+  const { rowCount } = await query('DELETE FROM users WHERE id = $1', [req.params.id]);
+  if (!rowCount) return res.status(404).json({ error: 'User not found' });
+  return res.status(204).end();
+});
+
+export default router;
diff --git a/backend/src/routes/auth.js b/backend/src/routes/auth.js
index 6de6c39..d551fc9 100644
--- a/backend/src/routes/auth.js
+++ b/backend/src/routes/auth.js
@@ -7,7 +7,18 @@ const router = Router();
 const EMAIL_RE = /^[^@\s]+@[^@\s]+\.[^@\s]+$/;
 
 function publicUser(row) {
-  return { id: row.id, email: row.email, name: row.name, isAdmin: !!row.is_admin, createdAt: row.created_at };
+  return {
+    id: row.id,
+    email: row.email,
+    name: row.name,
+    isAdmin: !!row.is_admin,
+    avatar: row.avatar || '',
+    locale: row.locale || 'en',
+    theme: row.theme || 'system',
+    bgImage: row.bg_image || '',
+    bgBlur: row.bg_blur !== false,
+    createdAt: row.created_at,
+  };
 }
 
 // POST /api/auth/register { email, name, password }
@@ -27,7 +38,7 @@ router.post('/register', async (req, res) => {
     if (existing.rowCount > 0) return res.status(409).json({ error: 'Email already registered' });
     const hash = await bcrypt.hash(String(password), 12);
     const { rows } = await query(
-      'INSERT INTO users (email, name, password_hash) VALUES ($1,$2,$3) RETURNING id, email, name, created_at',
+      'INSERT INTO users (email, name, password_hash) VALUES ($1,$2,$3) RETURNING id, email, name, is_admin, avatar, locale, theme, bg_image, bg_blur, created_at',
       [String(email).toLowerCase(), String(name).trim(), hash],
     );
     const token = signToken(rows[0]);
@@ -57,7 +68,7 @@ router.post('/login', async (req, res) => {
 
 // GET /api/auth/me
 router.get('/me', requireAuth, async (req, res) => {
-  const { rows } = await query('SELECT id, email, name, created_at FROM users WHERE id = $1', [req.user.id]);
+  const { rows } = await query('SELECT id, email, name, is_admin, avatar, locale, theme, bg_image, bg_blur, created_at FROM users WHERE id = $1', [req.user.id]);
   if (!rows[0]) return res.status(404).json({ error: 'User not found' });
   return res.json({ user: publicUser(rows[0]) });
 });
diff --git a/backend/src/routes/books.js b/backend/src/routes/books.js
new file mode 100644
index 0000000..e065118
--- /dev/null
+++ b/backend/src/routes/books.js
@@ -0,0 +1,71 @@
+import { Router } from 'express';
+import { query } from '../config/db.js';
+import { requireAuth } from '../middleware/auth.js';
+import { getRole } from './guards.js';
+
+const router = Router();
+router.use(requireAuth);
+
+// GET /api/books/by-workspace/:workspaceId
+router.get('/by-workspace/:workspaceId', async (req, res) => {
+  const role = await getRole(req.params.workspaceId, req.user.id);
+  if (!role) return res.status(403).json({ error: 'Not a workspace member' });
+  const { rows } = await query(
+    'SELECT * FROM books WHERE workspace_id = $1 ORDER BY position, updated_at DESC',
+    [req.params.workspaceId],
+  );
+  return res.json({ books: rows });
+});
+
+// POST /api/books { workspace_id, title?, icon? } (member+)
+router.post('/', async (req, res) => {
+  const { workspace_id, title = 'Untitled book', icon = '📚' } = req.body ?? {};
+  if (!workspace_id) return res.status(400).json({ error: 'workspace_id required' });
+  const role = await getRole(workspace_id, req.user.id);
+  if (role !== 'owner' && role !== 'admin' && role !== 'member') {
+    return res.status(403).json({ error: 'Viewers cannot create books' });
+  }
+  const { rows } = await query(
+    'INSERT INTO books (workspace_id, title, icon, created_by) VALUES ($1,$2,$3,$4) RETURNING *',
+    [workspace_id, String(title).slice(0, 200) || 'Untitled book', String(icon).slice(0, 20) || '📚', req.user.id],
+  );
+  return res.status(201).json({ book: rows[0] });
+});
+
+// PATCH /api/books/:id { title?, icon?, position? } (member+)
+router.patch('/:id', async (req, res) => {
+  const { rows: found } = await query('SELECT * FROM books WHERE id = $1', [req.params.id]);
+  const book = found[0];
+  if (!book) return res.status(404).json({ error: 'Not found' });
+  const role = await getRole(book.workspace_id, req.user.id);
+  if (role !== 'owner' && role !== 'admin' && role !== 'member') {
+    return res.status(403).json({ error: 'Viewers cannot edit' });
+  }
+  const { title, icon, position } = req.body ?? {};
+  const { rows } = await query(
+    `UPDATE books SET title = COALESCE($1, title), icon = COALESCE($2, icon),
+       position = COALESCE($3, position) WHERE id = $4 RETURNING *`,
+    [
+      title !== undefined ? String(title).slice(0, 200) : null,
+      icon !== undefined ? String(icon).slice(0, 20) : null,
+      position !== undefined ? Number(position) : null,
+      book.id,
+    ],
+  );
+  return res.json({ book: rows[0] });
+});
+
+// DELETE /api/books/:id (member+; pages inside are removed via FK cascade)
+router.delete('/:id', async (req, res) => {
+  const { rows: found } = await query('SELECT * FROM books WHERE id = $1', [req.params.id]);
+  const book = found[0];
+  if (!book) return res.status(404).json({ error: 'Not found' });
+  const role = await getRole(book.workspace_id, req.user.id);
+  if (role !== 'owner' && role !== 'admin' && role !== 'member') {
+    return res.status(403).json({ error: 'Viewers cannot delete' });
+  }
+  await query('DELETE FROM books WHERE id = $1', [book.id]);
+  return res.status(204).end();
+});
+
+export default router;
diff --git a/backend/src/routes/guards.js b/backend/src/routes/guards.js
index 7ee2ea8..e6c37bc 100644
--- a/backend/src/routes/guards.js
+++ b/backend/src/routes/guards.js
@@ -32,3 +32,10 @@ export async function getPageWithWorkspace(pageId) {
   const { rows } = await query('SELECT * FROM pages WHERE id = $1', [pageId]);
   return rows[0] || null;
 }
+
+/** Require global admin flag (set via web installer / admin dashboard). */
+export async function requireAdmin(req, res, next) {
+  const { rows } = await query('SELECT is_admin FROM users WHERE id = $1', [req.user.id]);
+  if (!rows[0]?.is_admin) return res.status(403).json({ error: 'Admin only' });
+  return next();
+}
diff --git a/backend/src/routes/pages.js b/backend/src/routes/pages.js
index 31cc6bd..d7004a5 100644
--- a/backend/src/routes/pages.js
+++ b/backend/src/routes/pages.js
@@ -30,24 +30,31 @@ router.get('/by-workspace/:workspaceId', async (req, res) => {
   return res.json({ pages: rows, role });
 });
 
-// POST /api/pages { workspace_id, parent_id?, title? }
+// POST /api/pages { workspace_id, parent_id?, book_id?, title? }
 router.post('/', async (req, res) => {
-  const { workspace_id, parent_id = null, title = 'Untitled' } = req.body ?? {};
+  const { workspace_id, parent_id = null, book_id = null, title = 'Untitled' } = req.body ?? {};
   if (!workspace_id) return res.status(400).json({ error: 'workspace_id required' });
   const role = await getRole(workspace_id, req.user.id);
   if (role !== 'owner' && role !== 'admin' && role !== 'member') {
     return res.status(403).json({ error: 'Viewers cannot create pages' });
   }
+  if (book_id) {
+    const { rows } = await query('SELECT id FROM books WHERE id = $1 AND workspace_id = $2', [book_id, workspace_id]);
+    if (!rows[0]) return res.status(400).json({ error: 'Invalid book_id' });
+  }
   if (parent_id) {
     const parent = await getPageWithWorkspace(parent_id);
     if (!parent || parent.workspace_id !== workspace_id) {
       return res.status(400).json({ error: 'Invalid parent_id' });
     }
+    if ((parent.book_id || null) !== (book_id || null)) {
+      return res.status(400).json({ error: 'Parent lives in a different book' });
+    }
   }
   const { rows } = await query(
-    `INSERT INTO pages (workspace_id, parent_id, title, created_by)
-     VALUES ($1,$2,$3,$4) RETURNING *`,
-    [workspace_id, parent_id, String(title).slice(0, 300) || 'Untitled', req.user.id],
+    `INSERT INTO pages (workspace_id, parent_id, book_id, title, created_by)
+     VALUES ($1,$2,$3,$4,$5) RETURNING *`,
+    [workspace_id, parent_id, book_id, String(title).slice(0, 300) || 'Untitled', req.user.id],
   );
   return res.status(201).json({ page: rows[0] });
 });
@@ -71,7 +78,7 @@ router.patch('/:id', async (req, res) => {
   const page = await getPageWithWorkspace(req.params.id);
   if (!page) return res.status(404).json({ error: 'Not found' });
   if (!(await canWrite(req.user.id, page))) return res.status(403).json({ error: 'Viewers cannot edit' });
-  const { title, icon, cover, content_json, content_html, position, parent_id, is_archived } = req.body ?? {};
+  const { title, icon, cover, content_json, content_html, position, parent_id, book_id, is_archived } = req.body ?? {};
   if (parent_id !== undefined && parent_id !== null) {
     if (parent_id === page.id) return res.status(400).json({ error: 'Page cannot be its own parent' });
     const parent = await getPageWithWorkspace(parent_id);
@@ -79,6 +86,10 @@ router.patch('/:id', async (req, res) => {
       return res.status(400).json({ error: 'Invalid parent_id' });
     }
   }
+  if (book_id !== undefined && book_id !== null) {
+    const { rows } = await query('SELECT id FROM books WHERE id = $1 AND workspace_id = $2', [book_id, page.workspace_id]);
+    if (!rows[0]) return res.status(400).json({ error: 'Invalid book_id' });
+  }
   const { rows } = await query(
     `UPDATE pages SET
        title = COALESCE($1, title),
@@ -88,6 +99,7 @@ router.patch('/:id', async (req, res) => {
        content_html = COALESCE($5, content_html),
        position = COALESCE($6, position),
        parent_id = CASE WHEN $8 THEN $7 ELSE parent_id END,
+       book_id = CASE WHEN $12 THEN $11 ELSE book_id END,
        is_archived = COALESCE($9, is_archived)
      WHERE id = $10 RETURNING *`,
     [
@@ -101,6 +113,8 @@ router.patch('/:id', async (req, res) => {
       parent_id !== undefined,
       is_archived !== undefined ? Boolean(is_archived) : null,
       page.id,
+      book_id !== undefined ? book_id : null,
+      book_id !== undefined,
     ],
   );
   const updated = rows[0];
diff --git a/backend/src/routes/tasks.js b/backend/src/routes/tasks.js
new file mode 100644
index 0000000..2fc58eb
--- /dev/null
+++ b/backend/src/routes/tasks.js
@@ -0,0 +1,128 @@
+import { Router } from 'express';
+import { query } from '../config/db.js';
+import { requireAuth } from '../middleware/auth.js';
+import { getRole } from './guards.js';
+
+const router = Router();
+router.use(requireAuth);
+const STATUSES = ['todo', 'doing', 'done'];
+const PRIORITIES = ['low', 'normal', 'high'];
+
+async function canWrite(userId, workspaceId) {
+  const role = await getRole(workspaceId, userId);
+  return role === 'owner' || role === 'admin' || role === 'member';
+}
+
+async function checkLinks(workspaceId, book_id, page_id) {
+  if (book_id) {
+    const { rows } = await query('SELECT id FROM books WHERE id = $1 AND workspace_id = $2', [book_id, workspaceId]);
+    if (!rows[0]) return 'Invalid book_id for this workspace';
+  }
+  if (page_id) {
+    const { rows } = await query('SELECT id FROM pages WHERE id = $1 AND workspace_id = $2', [page_id, workspaceId]);
+    if (!rows[0]) return 'Invalid page_id for this workspace';
+  }
+  return null;
+}
+
+// GET /api/tasks/by-workspace/:workspaceId?status=&from=&to=
+// from/to filter due_at (used by the calendar).
+router.get('/by-workspace/:workspaceId', async (req, res) => {
+  const role = await getRole(req.params.workspaceId, req.user.id);
+  if (!role) return res.status(403).json({ error: 'Not a workspace member' });
+  const { status, from, to } = req.query;
+  const conds = ['t.workspace_id = $1'];
+  const params = [req.params.workspaceId];
+  if (status && STATUSES.includes(String(status))) {
+    params.push(String(status));
+    conds.push(`t.status = $${params.length}`);
+  }
+  if (from) {
+    params.push(new Date(String(from)));
+    conds.push(`t.due_at >= $${params.length}`);
+  }
+  if (to) {
+    params.push(new Date(String(to)));
+    conds.push(`t.due_at <= $${params.length}`);
+  }
+  const { rows } = await query(
+    `SELECT t.*, b.title AS book_title, p.title AS page_title
+     FROM tasks t LEFT JOIN books b ON b.id = t.book_id LEFT JOIN pages p ON p.id = t.page_id
+     WHERE ${conds.join(' AND ')} ORDER BY t.due_at NULLS LAST, t.position, t.created_at`,
+    params,
+  );
+  return res.json({ tasks: rows });
+});
+
+// POST /api/tasks { workspace_id, book_id?, page_id?, title, status?, priority?, due_at? }
+router.post('/', async (req, res) => {
+  const { workspace_id, book_id = null, page_id = null, title = '', status = 'todo', priority = 'normal', due_at = null } = req.body ?? {};
+  if (!workspace_id) return res.status(400).json({ error: 'workspace_id required' });
+  if (!(await canWrite(req.user.id, workspace_id))) {
+    return res.status(403).json({ error: 'Viewers cannot create tasks' });
+  }
+  if (String(title).trim().length < 1 || String(title).length > 300) {
+    return res.status(400).json({ error: 'Title must be 1-300 chars' });
+  }
+  if (!STATUSES.includes(status)) return res.status(400).json({ error: 'Invalid status' });
+  if (!PRIORITIES.includes(priority)) return res.status(400).json({ error: 'Invalid priority' });
+  const linkErr = await checkLinks(workspace_id, book_id, page_id);
+  if (linkErr) return res.status(400).json({ error: linkErr });
+  const { rows } = await query(
+    `INSERT INTO tasks (workspace_id, book_id, page_id, title, status, priority, due_at, created_by)
+     VALUES ($1,$2,$3,$4,$5,$6,$7,$8) RETURNING *`,
+    [workspace_id, book_id, page_id, String(title).trim(), status, priority, due_at ? new Date(due_at) : null, req.user.id],
+  );
+  return res.status(201).json({ task: rows[0] });
+});
+
+// PATCH /api/tasks/:id
+router.patch('/:id', async (req, res) => {
+  const { rows: found } = await query('SELECT * FROM tasks WHERE id = $1', [req.params.id]);
+  const task = found[0];
+  if (!task) return res.status(404).json({ error: 'Not found' });
+  if (!(await canWrite(req.user.id, task.workspace_id))) {
+    return res.status(403).json({ error: 'Viewers cannot edit' });
+  }
+  const { title, status, priority, due_at, book_id, page_id, position } = req.body ?? {};
+  if (status !== undefined && !STATUSES.includes(status)) return res.status(400).json({ error: 'Invalid status' });
+  if (priority !== undefined && !PRIORITIES.includes(priority)) return res.status(400).json({ error: 'Invalid priority' });
+  if (title !== undefined && (String(title).trim().length < 1 || String(title).length > 300)) {
+    return res.status(400).json({ error: 'Title must be 1-300 chars' });
+  }
+  const nextBook = book_id !== undefined ? book_id : task.book_id;
+  const nextPage = page_id !== undefined ? page_id : task.page_id;
+  const linkErr = await checkLinks(task.workspace_id, nextBook, nextPage);
+  if (linkErr) return res.status(400).json({ error: linkErr });
+  const sets = [];
+  const params = [];
+  const push = (col, val) => { params.push(val); sets.push(`${col} = $${params.length}`); };
+  if (title !== undefined) push('title', String(title).trim());
+  if (status !== undefined) push('status', status);
+  if (priority !== undefined) push('priority', priority);
+  if (due_at !== undefined) push('due_at', due_at ? new Date(due_at) : null);
+  if (book_id !== undefined) push('book_id', book_id);
+  if (page_id !== undefined) push('page_id', page_id);
+  if (position !== undefined) push('position', Number(position));
+  if (sets.length === 0) return res.json({ task });
+  params.push(task.id);
+  const { rows } = await query(
+    `UPDATE tasks SET ${sets.join(', ')} WHERE id = $${params.length} RETURNING *`,
+    params,
+  );
+  return res.json({ task: rows[0] });
+});
+
+// DELETE /api/tasks/:id
+router.delete('/:id', async (req, res) => {
+  const { rows: found } = await query('SELECT * FROM tasks WHERE id = $1', [req.params.id]);
+  const task = found[0];
+  if (!task) return res.status(404).json({ error: 'Not found' });
+  if (!(await canWrite(req.user.id, task.workspace_id))) {
+    return res.status(403).json({ error: 'Viewers cannot delete' });
+  }
+  await query('DELETE FROM tasks WHERE id = $1', [task.id]);
+  return res.status(204).end();
+});
+
+export default router;
diff --git a/backend/src/routes/time.js b/backend/src/routes/time.js
new file mode 100644
index 0000000..1890ba1
--- /dev/null
+++ b/backend/src/routes/time.js
@@ -0,0 +1,116 @@
+import { Router } from 'express';
+import { query } from '../config/db.js';
+import { requireAuth } from '../middleware/auth.js';
+import { getRole } from './guards.js';
+
+const router = Router();
+router.use(requireAuth);
+
+function serialize(row) {
+  if (!row) return row;
+  return row;
+}
+
+// GET /api/time/by-workspace/:workspaceId — entries + currently running timer
+router.get('/by-workspace/:workspaceId', async (req, res) => {
+  const role = await getRole(req.params.workspaceId, req.user.id);
+  if (!role) return res.status(403).json({ error: 'Not a workspace member' });
+  const mine = req.query.mine === '1';
+  const params = [req.params.workspaceId];
+  let cond = 'e.workspace_id = $1';
+  if (mine) {
+    params.push(req.user.id);
+    cond += ` AND e.user_id = $${params.length}`;
+  }
+  const { rows } = await query(
+    `SELECT e.*, b.title AS book_title, p.title AS page_title, u.name AS user_name
+     FROM time_entries e
+     LEFT JOIN books b ON b.id = e.book_id
+     LEFT JOIN pages p ON p.id = e.page_id
+     LEFT JOIN users u ON u.id = e.user_id
+     WHERE ${cond} ORDER BY e.started_at DESC LIMIT 200`,
+    params,
+  );
+  const open = rows.find((r) => r.user_id === req.user.id && !r.ended_at) || null;
+  return res.json({ entries: rows, open });
+});
+
+// POST /api/time/start { workspace_id, book_id?, page_id?, description? }
+router.post('/start', async (req, res) => {
+  const { workspace_id, book_id = null, page_id = null, description = '' } = req.body ?? {};
+  if (!workspace_id) return res.status(400).json({ error: 'workspace_id required' });
+  const role = await getRole(workspace_id, req.user.id);
+  if (!role) return res.status(403).json({ error: 'Not a workspace member' });
+  const { rows: running } = await query(
+    'SELECT id FROM time_entries WHERE workspace_id = $1 AND user_id = $2 AND ended_at IS NULL',
+    [workspace_id, req.user.id],
+  );
+  if (running[0]) return res.status(409).json({ error: 'Timer already running', entry: running[0] });
+  const { rows } = await query(
+    `INSERT INTO time_entries (workspace_id, user_id, book_id, page_id, description)
+     VALUES ($1,$2,$3,$4,$5) RETURNING *`,
+    [workspace_id, req.user.id, book_id, page_id, String(description).slice(0, 500)],
+  );
+  return res.status(201).json({ entry: serialize(rows[0]) });
+});
+
+// POST /api/time/stop { workspace_id } — stops my running timer
+router.post('/stop', async (req, res) => {
+  const { workspace_id } = req.body ?? {};
+  if (!workspace_id) return res.status(400).json({ error: 'workspace_id required' });
+  const { rows } = await query(
+    `UPDATE time_entries SET ended_at = now(),
+       duration_seconds = EXTRACT(EPOCH FROM (now() - started_at))::int
+     WHERE id = (
+       SELECT id FROM time_entries
+       WHERE workspace_id = $1 AND user_id = $2 AND ended_at IS NULL
+       ORDER BY started_at DESC LIMIT 1
+     ) RETURNING *`,
+    [workspace_id, req.user.id],
+  );
+  if (!rows[0]) return res.status(404).json({ error: 'No running timer' });
+  return res.json({ entry: rows[0] });
+});
+
+// PATCH /api/time/:id { description?, book_id?, page_id? } (own or admin+)
+router.patch('/:id', async (req, res) => {
+  const { rows: found } = await query('SELECT * FROM time_entries WHERE id = $1', [req.params.id]);
+  const entry = found[0];
+  if (!entry) return res.status(404).json({ error: 'Not found' });
+  const role = await getRole(entry.workspace_id, req.user.id);
+  const { rows: me } = await query('SELECT is_admin FROM users WHERE id = $1', [req.user.id]);
+  if (entry.user_id !== req.user.id && !me[0]?.is_admin && role !== 'owner' && role !== 'admin') {
+    return res.status(403).json({ error: 'Forbidden' });
+  }
+  const { description, book_id, page_id } = req.body ?? {};
+  const { rows } = await query(
+    `UPDATE time_entries SET description = COALESCE($1, description),
+       book_id = CASE WHEN $4 THEN $2 ELSE book_id END,
+       page_id = CASE WHEN $5 THEN $3 ELSE page_id END
+     WHERE id = $6 RETURNING *`,
+    [
+      description !== undefined ? String(description).slice(0, 500) : null,
+      book_id !== undefined ? book_id : null,
+      page_id !== undefined ? page_id : null,
+      book_id !== undefined, page_id !== undefined,
+      entry.id,
+    ],
+  );
+  return res.json({ entry: rows[0] });
+});
+
+// DELETE /api/time/:id (own or admin+)
+router.delete('/:id', async (req, res) => {
+  const { rows: found } = await query('SELECT * FROM time_entries WHERE id = $1', [req.params.id]);
+  const entry = found[0];
+  if (!entry) return res.status(404).json({ error: 'Not found' });
+  const role = await getRole(entry.workspace_id, req.user.id);
+  const { rows: me } = await query('SELECT is_admin FROM users WHERE id = $1', [req.user.id]);
+  if (entry.user_id !== req.user.id && !me[0]?.is_admin && role !== 'owner' && role !== 'admin') {
+    return res.status(403).json({ error: 'Forbidden' });
+  }
+  await query('DELETE FROM time_entries WHERE id = $1', [entry.id]);
+  return res.status(204).end();
+});
+
+export default router;
diff --git a/backend/src/routes/users.js b/backend/src/routes/users.js
index 989cc10..326a57f 100644
--- a/backend/src/routes/users.js
+++ b/backend/src/routes/users.js
@@ -1,18 +1,111 @@
 import { Router } from 'express';
+import bcrypt from 'bcryptjs';
 import { query } from '../config/db.js';
 import { requireAuth } from '../middleware/auth.js';
 
 const router = Router();
 router.use(requireAuth);
 
-// GET /api/users/search?email= — find user by email (for invites)
+const LOCALES = ['de', 'en', 'zh'];
+const THEMES = ['light', 'dark', 'system'];
+
+// GET /api/users/search?email= — find user by exact email (for invites)
 router.get('/search', async (req, res) => {
   const { email = '' } = req.query;
   if (!email) return res.status(400).json({ error: 'email required' });
-  const { rows } = await query('SELECT id, email, name FROM users WHERE email = $1', [
-    String(email).toLowerCase(),
-  ]);
+  const { rows } = await query(
+    'SELECT id, email, name, avatar FROM users WHERE email = $1',
+    [String(email).toLowerCase()],
+  );
   return res.json({ user: rows[0] || null });
 });
 
+// GET /api/users/discover?q= — fuzzy user discovery for invites/mentions.
+// Returns id, name, email, avatar (never password hashes).
+router.get('/discover', async (req, res) => {
+  const q = String(req.query.q || '').trim().slice(0, 60);
+  if (q.length < 2) return res.json({ users: [] });
+  const { rows } = await query(
+    `SELECT id, name, email, avatar FROM users
+     WHERE name ILIKE $1 OR email ILIKE $1
+     ORDER BY name LIMIT 10`,
+    [`%${q}%`],
+  );
+  return res.json({ users: rows });
+});
+
+// PATCH /api/users/me — profile + appearance settings
+router.patch('/me', async (req, res) => {
+  const { name, email, avatar, locale, theme, bg_image, bg_blur } = req.body ?? {};
+  if (name !== undefined && (String(name).trim().length < 1 || String(name).length > 100)) {
+    return res.status(400).json({ error: 'Name must be 1-100 chars' });
+  }
+  if (email !== undefined && !/^[^@\s]+@[^@\s]+\.[^@\s]+$/.test(String(email))) {
+    return res.status(400).json({ error: 'Valid email required' });
+  }
+  if (locale !== undefined && !LOCALES.includes(locale)) {
+    return res.status(400).json({ error: 'Locale must be de, en or zh' });
+  }
+  if (theme !== undefined && !THEMES.includes(theme)) {
+    return res.status(400).json({ error: 'Theme must be light, dark or system' });
+  }
+  if (avatar !== undefined && String(avatar).length > 500) {
+    return res.status(400).json({ error: 'Avatar too long (max 500 chars, emoji or URL)' });
+  }
+  if (bg_image !== undefined && String(bg_image).length > 2000) {
+    return res.status(400).json({ error: 'Background URL too long' });
+  }
+  try {
+    const { rows } = await query(
+      `UPDATE users SET
+         name = COALESCE($1, name),
+         email = COALESCE($2, email),
+         avatar = COALESCE($3, avatar),
+         locale = COALESCE($4, locale),
+         theme = COALESCE($5, theme),
+         bg_image = COALESCE($6, bg_image),
+         bg_blur = COALESCE($7, bg_blur)
+       WHERE id = $8
+       RETURNING id, email, name, is_admin, avatar, locale, theme, bg_image, bg_blur, created_at`,
+      [
+        name !== undefined ? String(name).trim() : null,
+        email !== undefined ? String(email).toLowerCase() : null,
+        avatar !== undefined ? String(avatar).slice(0, 500) : null,
+        locale !== undefined ? locale : null,
+        theme !== undefined ? theme : null,
+        bg_image !== undefined ? String(bg_image).slice(0, 2000) : null,
+        bg_blur !== undefined ? Boolean(bg_blur) : null,
+        req.user.id,
+      ],
+    );
+    const u = rows[0];
+    return res.json({
+      user: {
+        id: u.id, email: u.email, name: u.name, isAdmin: !!u.is_admin,
+        avatar: u.avatar || '', locale: u.locale, theme: u.theme,
+        bgImage: u.bg_image || '', bgBlur: u.bg_blur !== false, createdAt: u.created_at,
+      },
+    });
+  } catch (err) {
+    if (err.code === '23505') return res.status(409).json({ error: 'Email already taken' });
+    console.error('[users/me]', err.message);
+    return res.status(500).json({ error: 'Update failed' });
+  }
+});
+
+// PATCH /api/users/me/password { currentPassword, newPassword }
+router.patch('/me/password', async (req, res) => {
+  const { currentPassword = '', newPassword = '' } = req.body ?? {};
+  if (String(newPassword).length < 8) {
+    return res.status(400).json({ error: 'New password must be at least 8 chars' });
+  }
+  const { rows } = await query('SELECT password_hash FROM users WHERE id = $1', [req.user.id]);
+  if (!rows[0]) return res.status(404).json({ error: 'User not found' });
+  const ok = await bcrypt.compare(String(currentPassword), rows[0].password_hash);
+  if (!ok) return res.status(401).json({ error: 'Current password is wrong' });
+  const hash = await bcrypt.hash(String(newPassword), 12);
+  await query('UPDATE users SET password_hash = $1 WHERE id = $2', [hash, req.user.id]);
+  return res.json({ ok: true });
+});
+
 export default router;
diff --git a/backend/src/routes/workspaces.js b/backend/src/routes/workspaces.js
index 5ab2fcd..863df41 100644
--- a/backend/src/routes/workspaces.js
+++ b/backend/src/routes/workspaces.js
@@ -59,7 +59,7 @@ router.delete('/:id', requireWorkspace('owner'), async (req, res) => {
 // GET /api/workspaces/:id/members
 router.get('/:id/members', requireWorkspace('viewer'), async (req, res) => {
   const { rows } = await query(
-    `SELECT u.id, u.email, u.name, m.role, m.created_at
+    `SELECT u.id, u.email, u.name, u.avatar, m.role, m.created_at
      FROM workspace_members m JOIN users u ON u.id = m.user_id
      WHERE m.workspace_id = $1 ORDER BY m.created_at`,
     [req.params.id],