Multi-user sharing, groups, and in-app notifications

Backend:
- Alembic migration 0025: groups, group_memberships, project_shares,
  note_shares, notifications tables
- models: Group, GroupMembership, ProjectShare, NoteShare, Notification
- services/access.py: permission resolution (viewer/editor/admin/owner)
- services/groups.py + routes/groups.py: full group CRUD + membership
- services/sharing.py + routes/shares.py: project/note sharing API
- services/notifications.py: in-app notification create/list/mark-read
- routes/in_app_notifications.py: GET/POST notification endpoints
- routes/users.py: user search endpoint
- services/projects.py + services/notes.py: *_for_user variants
- routes updated to use *_for_user on get/list; adds permission field
- app.py: register all new blueprints

Frontend:
- api/client.ts: ShareEntry, GroupEntry, NotificationEntry types + helpers
- stores/notifications.ts: Pinia store with polling
- NotificationBell.vue: bell icon + badge + dropdown toggle + 60s poll
- NotificationsPanel.vue: unread notification list with mark-all-read
- ShareDialog.vue: teleport modal for sharing projects/notes with users/groups
- SharedWithMeView.vue: /shared route listing shared projects and notes
- AppHeader: NotificationBell, Shared nav link
- ProjectView, NoteViewerView, TaskViewerView: Share button + ShareDialog
- SettingsView: Groups admin tab with create/delete groups + member mgmt
- router: /shared route

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/fabledassistant/routes/notes.py

@@ -26,6 +26,7 @@ from fabledassistant.services.notes import (
     get_backlinks,
     get_note,
     get_note_by_title,
+    get_note_for_user,
     get_or_create_note_by_title,
     list_notes,
     update_note,
@@ -189,10 +190,13 @@ async def resolve_title_route():
 @login_required
 async def get_note_route(note_id: int):
     uid = get_current_user_id()
-    note = await get_note(uid, note_id)
-    if note is None:
+    result = await get_note_for_user(uid, note_id)
+    if result is None:
         return not_found("Note")
-    return jsonify(note.to_dict())
+    note, permission = result
+    data = note.to_dict()
+    data["permission"] = permission
+    return jsonify(data)
 
 
 @notes_bp.route("/<int:note_id>", methods=["PUT"])