Add search, offline queue, app icon, and UI polish

- Collapsible search in notes and tasks: magnifying glass in AppBar
  expands to a text field inline; close button resets the filter
- Offline capture queue: failed quick-captures (NetworkException) are
  persisted to SharedPreferences and retried automatically on next
  successful submit or app start; badge shows pending count
- App icon: book-with-sparkle logo from FabledAssistant SVG rendered
  at all Android densities with adaptive icon (indigo #6366f1 bg)
- Dark mode subtitle fix: use colorScheme.onSurfaceVariant for note
  preview and conversation timestamp text
- Remove swipe-to-delete (accidental deletions); long-press remains
- Chat: SSE streaming reliability, polling fallback, title patching
- Settings: theme toggle (system/light/dark) persisted to prefs
- Notes: delete button in edit screen; body preview in list
- Tasks: fix delete dialog context; description search support

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

lib/providers/capture_queue_provider.dart

@@ -0,0 +1,29 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+import 'settings_provider.dart';
+
+final captureQueueProvider =
+    StateNotifierProvider<CaptureQueueNotifier, List<String>>(
+  (ref) => CaptureQueueNotifier(ref.watch(sharedPreferencesProvider)),
+);
+
+class CaptureQueueNotifier extends StateNotifier<List<String>> {
+  static const _key = 'capture_queue';
+  final SharedPreferences _prefs;
+
+  CaptureQueueNotifier(this._prefs)
+      : super(_prefs.getStringList(_key) ?? []);
+
+  Future<void> enqueue(String text) async {
+    final updated = [...state, text];
+    await _prefs.setStringList(_key, updated);
+    state = updated;
+  }
+
+  Future<void> dequeue(String text) async {
+    final updated = List<String>.from(state)..remove(text);
+    await _prefs.setStringList(_key, updated);
+    state = updated;
+  }
+}