feat(frontend): bell, chat, uploads, glass, teams UI, fixes

- Notification bell with invites (accept/decline refreshes workspaces)
  and unread badge (polling + socket push); team chat view realtime
- Avatar/background uploads in settings + glassmorphism widgets toggle;
  background layer resolves /uploads URLs; full-bleed blurred backdrop
- Sidebar: visible creation errors, working sub-pages (parent_id),
  TEAM badge workspaces, refresh button, chat nav; admin creates users
- Tasks: per-team boards, assignee select with avatars; admin tabs for
  users/teams/groups (team workspaces, permission checkboxes)
- Register view removed (admin-only accounts); login localized;
  prettier emoji set; scaling/overflow + mobile fixes

README.md

@@ -15,7 +15,14 @@ light/dark mode. Self-hostable via Node.js or Docker Compose.
 - **Pages** — Nested pages (`parent_id`) in workspaces or **books**, icon + cover,
   ordering, TipTap rich-text with **tables + checklists**, stored as JSON + HTML.
 - **Books** 📚 — Independent containers for pages, collapsible in the sidebar.
-- **Tasks** ✅ — Kanban (todo/doing/done), priorities, deadlines, links to books/pages.
+- **Tasks** ✅ — Kanban (todo/doing/doing→done), priorities, deadlines, **assignees**,
+  links to books/pages, **per-team boards**.
+- **Teams** 👥 — Teams with managers/members, **own workspaces** (`TEAM_"name"` badge),
+  permission **groups** (e.g. Team Creators: teams.create/edit/invite, workspace.invite).
+- **Invites + notifications** 🔔 — Pending invites with accept/decline, bell with unread
+  badge (polling + realtime push), notifications for invites and chat messages.
+- **Team chat** 💬 — Realtime workspace channel via Socket.IO.
+- **Uploads** 📤 — Avatar/background images uploadable (served from `/uploads`).
 - **Calendar** 🗓️ — Deadlines from tasks appear automatically.
 - **Time tracking** ⏱️ — Top-right timer, entries linkable to books, history list.
 - **Settings window** ⚙️ — Profile (name, email, avatar, password), appearance