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/templates/collections.html

@@ -36,6 +36,18 @@
                     <option value="dynamic">Dynamic (query-based)</option>
                 </select>
             </div>
+            <div id="query-builder-section" style="display: none;">
+                <div class="form-group">
+                    <label for="collection-query">Query Expression</label>
+                    <input type="text" id="collection-query" placeholder="e.g. personal AND lan NOT ai">
+                    <small class="form-hint">Supports: AND, OR, XOR, parentheses, field filters (tag:, url:, title:)</small>
+                </div>
+                <div class="form-actions" style="margin-top: 0; margin-bottom: 1rem;">
+                    <button type="button" class="btn btn-sm btn-secondary" id="preview-query-btn">Preview Results</button>
+                    <span id="query-status" class="query-status"></span>
+                </div>
+                <div id="query-preview-results" class="query-preview" style="display: none;"></div>
+            </div>
             <div class="form-group checkbox-group">
                 <label>
                     <input type="checkbox" id="collection-public">
@@ -64,5 +76,5 @@
 {% endblock %}
 
 {% block extra_js %}
-<script src="/static/js/collections-page.js"></script>
+<script src="/static/js/collections-page.js?v={{ build_id }}"></script>
 {% endblock %}