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.

pubspec.yaml

@@ -44,6 +44,10 @@ dependencies:
   flutter_secure_storage: ^10.2.0
   local_auth: ^3.0.1
   sqlite3: ^3.3.1
+  http: ^0.13.6
+  crypto: ^3.0.6
+  cryptography: ^2.7.0
+  uuid: ^4.0.0
 
 dev_dependencies:
   flutter_test:
@@ -70,7 +74,7 @@ flutter:
   # the material Icons class.
   uses-material-design: true
 
-assets:
+  assets:
     - assets/icon.png
 
 hooks: