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

frontend/src/views/PageEditor.vue

@@ -158,7 +158,7 @@ onUnmounted(() => {
         <button class="ghost" @click="editor?.chain().focus().toggleHeading({ level: 2 }).run()">H2</button>
         <button class="ghost" @click="editor?.chain().focus().toggleBulletList().run()">• {{ L.t('side.pages') }}</button>
         <button class="ghost" @click="editor?.chain().focus().toggleTaskList().run()">☑️</button>
-        <button class="ghost" @click="editor?.chain().focus().insertTable({ rows: 3, cols: 3 }).run()">▦ Table</button>
+        <button class="ghost" @click="editor?.chain().focus().insertTable({ rows: 3, cols: 3 }).run()">⊞ Table</button>
         <button class="ghost" @click="editor?.chain().focus().toggleCodeBlock().run()">&lt;/&gt;</button>
         <button @click="save()">💾 {{ L.t('c.save') }}</button>
       </div>