Refactor theme colors and styles across the application

- Introduced AppColors class to centralize color definitions for better maintainability and consistency.
- Updated various screens (Settings, Vault Access, Note Card, etc.) to use AppColors for styling instead of hardcoded colors.
- Enhanced UI elements with improved color contrast and accessibility.
- Replaced gradient backgrounds with defined color schemes for a cohesive look.
- Refactored button styles and text colors to align with the new theme structure.

lib/widgets/sync_status_indicator.dart

@@ -1,4 +1,5 @@
 import 'package:flutter/material.dart';
+import 'package:notas/theme/app_colors.dart';
 import 'package:notas/widgets/sync_status.dart';
 
 class SyncStatusIndicator extends StatelessWidget {
@@ -91,7 +92,11 @@ class SyncStatusIndicator extends StatelessWidget {
         return Tooltip(
           message: _messageForStatus(),
           child: _buildIndicator(
-            const Icon(Icons.cloud_outlined, size: 16, color: Colors.white38),
+            const Icon(
+              Icons.cloud_outlined,
+              size: 16,
+              color: AppColors.textSubtle,
+            ),
           ),
         );
 
@@ -101,7 +106,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.sync,
-              color: const Color.fromARGB(255, 165, 165, 165),
+              color: AppColors.syncPreparing,
               determinate: false,
             ),
           ),
@@ -113,7 +118,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.cloud_upload_outlined,
-              color: const Color.fromARGB(255, 109, 191, 255),
+              color: AppColors.syncEncrypting,
               determinate: true,
             ),
           ),
@@ -125,7 +130,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.cloud_upload,
-              color: const Color.fromARGB(255, 98, 190, 255),
+              color: AppColors.syncUploading,
               determinate: false,
             ),
           ),
@@ -137,7 +142,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.cloud_sync_outlined,
-              color: const Color.fromARGB(255, 150, 150, 150),
+              color: AppColors.syncWaiting,
               determinate: false,
             ),
           ),
@@ -149,7 +154,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.cloud_download_outlined,
-              color: const Color.fromARGB(255, 154, 194, 112),
+              color: AppColors.syncDecrypting,
               determinate: true,
             ),
           ),
@@ -161,7 +166,7 @@ class SyncStatusIndicator extends StatelessWidget {
           child: _buildIndicator(
             _buildStatusBadge(
               icon: Icons.sync,
-              color: const Color.fromARGB(255, 150, 150, 150),
+              color: AppColors.syncWaiting,
               determinate: false,
             ),
           ),
@@ -171,7 +176,7 @@ class SyncStatusIndicator extends StatelessWidget {
         return Tooltip(
           message: _messageForStatus(),
           child: _buildIndicator(
-            const Icon(Icons.check_circle, size: 16, color: Colors.green),
+            const Icon(Icons.check_circle, size: 16, color: AppColors.success),
           ),
         );
 
@@ -179,7 +184,7 @@ class SyncStatusIndicator extends StatelessWidget {
         return Tooltip(
           message: _messageForStatus(),
           child: _buildIndicator(
-            const Icon(Icons.error, size: 16, color: Colors.red),
+            const Icon(Icons.error, size: 16, color: AppColors.destructive),
           ),
         );
     }