Refactor theme management: Replace AppColors with AppPalette

- Removed AppColors class and migrated all references to AppPalette.
- Updated VaultAccessScreen, MenuDrawer, NoteCard, SearchAppBar, and other widgets to use AppPalette for color management.
- Introduced AppPalette to handle light and dark themes with appropriate color schemes.
- Adjusted theme application in AppTheme to utilize AppPalette extensions.
- Updated tests to reflect changes in theme structure and color references.

lib/widgets/sync_status_indicator.dart

@@ -1,5 +1,5 @@
 import 'package:flutter/material.dart';
-import 'package:notas/theme/app_colors.dart';
+import 'package:notas/theme/app_palette.dart';
 import 'package:notas/widgets/sync_status.dart';
 
 class SyncStatusIndicator extends StatelessWidget {
@@ -87,16 +87,14 @@ class SyncStatusIndicator extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final AppPalette palette = Theme.of(context).extension<AppPalette>()!;
+
     switch (status) {
       case SyncStatus.idle:
         return Tooltip(
           message: _messageForStatus(),
           child: _buildIndicator(
-            const Icon(
-              Icons.cloud_outlined,
-              size: 16,
-              color: AppColors.textSubtle,
-            ),
+            Icon(Icons.cloud_outlined, size: 16, color: palette.textSecondary),
           ),
         );
 
@@ -106,7 +104,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.sync,
-              color: AppColors.syncPreparing,
+              color: palette.syncPreparing,
               determinate: false,
             ),
           ),
@@ -118,7 +116,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.cloud_upload_outlined,
-              color: AppColors.syncEncrypting,
+              color: palette.syncEncrypting,
               determinate: true,
             ),
           ),
@@ -130,7 +128,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.cloud_upload,
-              color: AppColors.syncUploading,
+              color: palette.syncUploading,
               determinate: false,
             ),
           ),
@@ -142,7 +140,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.cloud_sync_outlined,
-              color: AppColors.syncWaiting,
+              color: palette.syncWaiting,
               determinate: false,
             ),
           ),
@@ -154,7 +152,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.cloud_download_outlined,
-              color: AppColors.syncDecrypting,
+              color: palette.syncDecrypting,
               determinate: true,
             ),
           ),
@@ -166,7 +164,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.sync,
-              color: AppColors.syncWaiting,
+              color: palette.syncWaiting,
               determinate: false,
             ),
           ),
@@ -176,7 +174,7 @@ class SyncStatusIndicator extends StatelessWidget {
         return Tooltip(
           message: _messageForStatus(),
           child: _buildIndicator(
-            const Icon(Icons.check_circle, size: 16, color: AppColors.success),
+            Icon(Icons.check_circle, size: 16, color: palette.success),
           ),
         );
 
@@ -184,7 +182,7 @@ class SyncStatusIndicator extends StatelessWidget {
         return Tooltip(
           message: _messageForStatus(),
           child: _buildIndicator(
-            const Icon(Icons.error, size: 16, color: AppColors.destructive),
+            Icon(Icons.error, size: 16, color: palette.destructiveAccent),
           ),
         );
     }