feat: add web UI, query engine, session management, and 20 E2E tests

- Web UI: login, dashboard, links CRUD, collections, API keys, admin pages
- Query engine: AND/OR/XOR with field filters, tag search, preview endpoint
- Session management: token expiry detection, 401 interceptor, expiry banner
- Links search: tags included, multi-word AND, query mode with set operations
- Collections: static/dynamic, query builder with preview, public tree view
- Save as Collection: convert search results (static) or query (dynamic)
- Dashboard stats: resilient loading with allSettled pattern
- Login page: redesigned with public collections tree view
- Bug fix: query executor None fields crash (notes/description/url/title)
- E2E tests: 20 Playwright tests covering all critical user flows
- All 104 tests passing (84 unit/integration + 20 E2E)

LinkSyncServer/tasks.md

@@ -153,3 +153,55 @@
 - [x] User guide (README.md)
 - [x] Query syntax guide (README.md)
 - [x] Deployment guide (README.md)
+
+## Phase 9: Web Interface Enhancements
+
+### Session Management
+- [x] Token expiry detection on page load
+- [x] 401 interceptor for all API calls
+- [x] Session expiry warning banner (<2 minutes)
+- [x] Graceful redirect to login on expiry
+- [x] Session expired message on login page
+
+### Dashboard
+- [x] Stats display with numbers (never `-`)
+- [x] Quick actions grid
+- [x] Admin section visibility toggle
+- [x] Resilient stats loading (allSettled pattern)
+
+### Links Page
+- [x] Simple search mode (keyword across all fields)
+- [x] Query mode toggle (set operations)
+- [x] Multi-word AND search
+- [x] Tag search inclusion
+- [x] Save as Collection feature (static and dynamic)
+- [x] Query preview with result count
+
+### Collections Page
+- [x] Query builder UI for dynamic collections
+- [x] Query preview button
+- [x] Result count display
+- [x] Query expression display on cards
+- [x] Type selector toggles query section
+
+### API Keys Page
+- [x] Create API key modal
+- [x] Delete API key confirmation
+
+### Admin Page
+- [x] User CRUD interface
+- [x] Role assignment
+- [x] System statistics
+- [x] Audit log viewer
+
+## Phase 10: Testing
+
+### E2E Tests (Playwright)
+- [x] Install Playwright and pytest-playwright
+- [x] Auth flow tests (login, dashboard, logout, expiry)
+- [x] Link CRUD tests
+- [x] Search tests (simple, multi-word, by tag, query mode)
+- [x] Collection tests (static, dynamic with query, delete)
+- [x] Save as Collection tests (static and dynamic)
+- [x] API Key tests (create, delete)
+- [x] Admin tests (user management)