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.lock

@@ -162,13 +162,21 @@ packages:
     source: hosted
     version: "3.1.2"
   crypto:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: crypto
       sha256: c8ea0233063ba03258fbcf2ca4d6dadfefe14f02fab57702265467a19f27fadf
       url: "https://pub.dev"
     source: hosted
     version: "3.0.7"
+  cryptography:
+    dependency: "direct main"
+    description:
+      name: cryptography
+      sha256: "3eda3029d34ec9095a27a198ac9785630fe525c0eb6a49f3d575272f8e792ef0"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.9.0"
   cupertino_icons:
     dependency: "direct main"
     description:
@@ -360,6 +368,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.0.3"
+  http:
+    dependency: "direct main"
+    description:
+      name: http
+      sha256: "5895291c13fa8a3bd82e76d5627f69e0d85ca6a30dcac95c4ea19a5d555879c2"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.13.6"
   http_multi_server:
     dependency: transitive
     description:
@@ -893,6 +909,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.4.0"
+  uuid:
+    dependency: "direct main"
+    description:
+      name: uuid
+      sha256: "1fef9e8e11e2991bb773070d4656b7bd5d850967a2456cfc83cf47925ba79489"
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.5.3"
   vector_math:
     dependency: transitive
     description: