Redesign doc service UX for scale + add group-based document sharing

- Three-column layout: Sidebar + SourcePanel (views + searchable category tree) + main
- DocumentSlideOver (480px right panel): inline editing, type picker, AI suggestion confirm/reject,
  categories combobox, tags editor, sharing section, raw text, re-analyse/delete actions
- ManageCategoriesDialog: inline rename, delete with confirm, search filter
- DocumentsPage rewrite: filter chip system, multi-file upload queue, drag-and-drop overlay,
  bulk actions bar (share/delete), smart TanStack Query polling, URL-driven view state
- Sidebar simplified: per-category NavLinks removed; Documents = single NavLink under Apps
- Backend: document_shares table (migration 0004), share CRUD endpoints, shared-with-me view,
  N+1-safe share_count via GROUP BY, recipient download access, X-User-Groups header enforcement
- Gateway proxy: injects X-User-Groups header into all document + category proxy requests
- Backend users: GET /api/users/me/groups endpoint for share picker combobox
- CLAUDE.md, STATUS.md files, and changelog updated

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

features/doc-service/app/deps.py

@@ -10,3 +10,14 @@ async def get_user_id(x_user_id: str = Header(...)) -> str:
     if not x_user_id:
         raise HTTPException(status_code=400, detail="Missing X-User-Id header")
     return x_user_id
+
+
+async def get_user_groups(x_user_groups: str = Header(default="")) -> list[str]:
+    """
+    Extract the group IDs injected by the main backend proxy.
+    Comma-separated list of group UUIDs the current user belongs to.
+    Returns an empty list if the header is absent or empty.
+    """
+    if not x_user_groups:
+        return []
+    return [g.strip() for g in x_user_groups.split(",") if g.strip()]