feat: Implement note encryption and synchronization features

- Added NoteEncryption class for encrypting and decrypting note content using AES-GCM.
- Updated NoteRepository to handle synchronization of notes and categories with the server, including encryption of note data before sending.
- Introduced SyncRequest and SyncResponse models for managing synchronization data.
- Enhanced LocalVaultService to store and retrieve the encryption key.
- Modified HomeScreen and SettingsScreen to trigger synchronization after note operations and manage API endpoint settings.
- Added SyncStatusIndicator to provide visual feedback on synchronization status in the app title bar.
- Created Category model to manage note categories with encryption support.
- Updated note model to include UUID, server version, deletion status, and category ID.
- Added necessary UI elements for displaying and managing the encryption key in SettingsScreen.
- Updated dependencies in pubspec.yaml for cryptography and HTTP handling.

lib/screens/home_screen.dart

@@ -75,6 +75,12 @@ class _HomeScreenState extends State<HomeScreen> {
       setState(() {
         _notes = updatedNotes;
       });
+
+      // Trigger sync after creating a note and refresh local list
+      try {
+        await widget.repository.performSync();
+        await _loadNotes();
+      } catch (_) {}
     }
   }
 
@@ -92,6 +98,12 @@ class _HomeScreenState extends State<HomeScreen> {
     setState(() {
       _notes = updatedNotes;
     });
+
+    // Trigger sync after deleting a note and refresh local list
+    try {
+      await widget.repository.performSync();
+      await _loadNotes();
+    } catch (_) {}
   }
 
   Future<void> _reorderNote(int oldIndex, int newIndex) async {
@@ -140,6 +152,11 @@ class _HomeScreenState extends State<HomeScreen> {
         setState(() {
           _notes = _normalizeNotes(updatedNotes);
         });
+        // Trigger sync after editing a note and refresh local list
+        try {
+          await widget.repository.performSync();
+          await _loadNotes();
+        } catch (_) {}
       }
     }
   }
@@ -172,9 +189,16 @@ class _HomeScreenState extends State<HomeScreen> {
         ? const Center(child: CircularProgressIndicator())
         : _notes.isEmpty
             ? const _EmptyState()
-            : MouseRegion(
-                cursor: _isDragging ? SystemMouseCursors.grabbing : SystemMouseCursors.basic,
-                child: MasonryGridView.count(
+            : RefreshIndicator(
+                onRefresh: () async {
+                  try {
+                    await widget.repository.performSync();
+                  } catch (_) {}
+                  await _loadNotes();
+                },
+                child: MouseRegion(
+                  cursor: _isDragging ? SystemMouseCursors.grabbing : SystemMouseCursors.basic,
+                  child: MasonryGridView.count(
                   crossAxisCount: crossAxisCount,
                   mainAxisSpacing: 10,
                   crossAxisSpacing: 10,
@@ -296,7 +320,8 @@ class _HomeScreenState extends State<HomeScreen> {
                     );
                   },
                 ),
-              );
+              ),
+            );
 
     return Scaffold(
       body: Container(