Add sidebar app sub-nav with categories, category filter, and re-analysis on category creation

- Sidebar: Apps accordion expands to Documents, which expands to list all
  user categories; clicking a category navigates to /apps/documents?category_id=<id>
- DocumentsPage: reads category_id from URL and applies filter; shows active
  category chip in FilterBar with dismiss; removed TagEditor (deferred)
- doc-service GET /documents: new category_id query param filters via subquery
- doc-service POST /documents/categories: detects similar category names and
  triggers background re-analysis of affected documents so the new category
  surfaces as a pending AI suggestion on relevant docs

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

frontend/STATUS.md

@@ -39,6 +39,14 @@ Cards for each installed app:
 - **Documents** — link to `/apps/documents`; admin gear icon → `/apps/documents/settings/admin`
 - **AI Service** — infrastructure card; admin gear icon → `/apps/ai/settings/admin`; no Open button (no user-facing UI)
 
+### Sidebar navigation
+
+`Apps` is an expandable accordion in the sidebar:
+- **Documents** sub-item (expandable) — lists all user categories beneath it; clicking a category navigates to `/apps/documents?category_id=<id>`
+- AI Service is not listed (no openable UI)
+- Sections auto-open when navigating to their route
+- In collapsed (icons-only) mode, clicking the Apps icon navigates to `/apps`
+
 ### Documents page (`/apps/documents`)
 
 **Upload:** PDF file input, 202 response, error display.
@@ -63,7 +71,6 @@ Cards for each installed app:
 - Delete button (confirm dialog)
 
 **Document row (expanded):**
-- **Tag editor** — read mode shows chips + Edit button; edit mode has removable chips + input (Enter/comma to add) + Save/Cancel
 - **Extracted data table** — all AI-extracted JSON fields (excludes `tags`, `suggested_categories`)
 - **Error message** — shown if status=failed
 - **Categories** — assigned chips with remove; dropdown to assign existing; AI-suggested chips with Accept / Create & Assign / Dismiss
@@ -98,7 +105,7 @@ Key functions:
 
 | Function | Description |
 |----------|-------------|
-| `listDocuments(params)` | `GET /documents` — returns `DocumentPage` |
+| `listDocuments(params)` | `GET /documents` — returns `DocumentPage`; supports `category_id` filter |
 | `uploadDocument(file)` | `POST /documents/upload` |
 | `deleteDocument(id)` | `DELETE /documents/{id}` |
 | `downloadDocument(id, filename)` | Blob URL download |