feat: add biometric authentication support and related UI screens

- Updated AndroidManifest.xml to include permissions for biometric authentication.
- Changed MainActivity to extend FlutterFragmentActivity for better compatibility.
- Modified gradle.properties to optimize memory settings.
- Enhanced app.dart to manage new app phases for biometric authentication.
- Implemented LocalVaultService methods for handling biometric key protection.
- Created BiometricChoiceScreen and BiometricGateScreen for user interaction.
- Updated HomeScreen to handle vault invalidation scenarios.
- Registered local_auth plugin for biometric functionality on macOS and Windows.
- Updated pubspec.yaml and pubspec.lock to include local_auth dependency.

lib/screens/home_screen.dart

@@ -15,10 +15,12 @@ class HomeScreen extends StatefulWidget {
     super.key,
     required this.repository,
     required this.onOpenSettings,
+    this.onVaultInvalid,
   });
 
   final NoteRepository repository;
   final VoidCallback onOpenSettings;
+  final Future<void> Function()? onVaultInvalid;
 
   @override
   State<HomeScreen> createState() => _HomeScreenState();
@@ -38,16 +40,21 @@ class _HomeScreenState extends State<HomeScreen> {
   }
 
   Future<void> _loadNotes() async {
-    final List<Note> storedNotes = await widget.repository.loadNotes();
+    try {
+      final List<Note> storedNotes = await widget.repository.loadNotes();
 
-    if (!mounted) {
-      return;
+      if (!mounted) return;
+
+      setState(() {
+        _notes = storedNotes;
+        _isLoading = false;
+      });
+    } catch (e) {
+      // If loading notes fails (e.g., DB corrupt), notify the app to reset the vault.
+      if (widget.onVaultInvalid != null) {
+        await widget.onVaultInvalid!();
+      }
     }
-
-    setState(() {
-      _notes = storedNotes;
-      _isLoading = false;
-    });
   }
 
   Future<void> _openNoteComposer() async {