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/screens/chat/chat_screen.dart

@@ -50,6 +50,12 @@ class _ChatScreenState extends ConsumerState<ChatScreen> {
         ScaffoldMessenger.of(context)
             .showSnackBar(SnackBar(content: Text(e.message)));
       }
+    } catch (_) {
+      if (mounted) {
+        ScaffoldMessenger.of(context).showSnackBar(
+          const SnackBar(content: Text('Failed to send message.')),
+        );
+      }
     }
   }
 
@@ -63,15 +69,26 @@ class _ChatScreenState extends ConsumerState<ChatScreen> {
       _scrollToBottom();
     });
 
+    final convTitle = ref
+        .watch(conversationsProvider)
+        .valueOrNull
+        ?.where((c) => c.id == widget.conversationId)
+        .firstOrNull
+        ?.title;
+
     return Scaffold(
-      appBar: AppBar(title: const Text('Chat')),
+      appBar: AppBar(
+        title: Text(convTitle?.isNotEmpty == true ? convTitle! : 'Chat'),
+      ),
       body: Column(
         children: [
           Expanded(
             child: messagesAsync.when(
               loading: () =>
                   const Center(child: CircularProgressIndicator()),
-              error: (e, _) => Center(child: Text('Error: $e')),
+              error: (_, _) => const Center(
+                child: Text('Could not load messages.'),
+              ),
               data: (messages) {
                 if (messages.isEmpty) {
                   return const Center(