refactor(apps): 主题系统迁移至 ColorScheme + 扩展架构并支持 Dark Mode

apps/lib/features/contacts/presentation/screens/add_contact_screen.dart

@@ -34,8 +34,9 @@ class _AddContactScreenState extends State<AddContactScreen> {
 
   @override
   Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
     return Scaffold(
-      backgroundColor: AppColors.surfaceSecondary,
+      backgroundColor: colorScheme.surfaceContainerLow,
       resizeToAvoidBottomInset: false,
       body: SafeArea(
         maintainBottomViewPadding: true,
@@ -73,6 +74,7 @@ class _AddContactScreenState extends State<AddContactScreen> {
   }
 
   Widget _buildConfirmButton() {
+    final colorScheme = Theme.of(context).colorScheme;
     return SizedBox(
       width: AppSpacing.xxl * 2,
       height: AppSpacing.xxl * 2,
@@ -80,47 +82,45 @@ class _AddContactScreenState extends State<AddContactScreen> {
         onPressed: _handleConfirm,
         style: TextButton.styleFrom(
           padding: const EdgeInsets.all(AppSpacing.none),
-          backgroundColor: AppColors.surfaceInfo,
+          backgroundColor: colorScheme.primaryContainer,
           shape: RoundedRectangleBorder(
             borderRadius: BorderRadius.circular(AppRadius.full),
-            side: const BorderSide(color: AppColors.borderQuaternary),
+            side: BorderSide(color: colorScheme.outlineVariant),
           ),
         ),
-        child: const Icon(
+        child: Icon(
           Icons.check,
           size: AppSpacing.lg,
-          color: AppColors.blue600,
+          color: colorScheme.primary,
         ),
       ),
     );
   }
 
   Widget _buildAvatarSection() {
+    final colorScheme = Theme.of(context).colorScheme;
     return Center(
       child: Container(
         width: 72,
         height: 72,
         decoration: BoxDecoration(
-          color: AppColors.surfaceInfoLight,
+          color: colorScheme.primaryContainer.withValues(alpha: 0.45),
           borderRadius: BorderRadius.circular(36),
-          border: Border.all(color: Colors.transparent),
-        ),
-        child: const Icon(
-          Icons.person_outline,
-          size: 24,
-          color: AppColors.slate400,
+          border: Border.all(color: colorScheme.surface.withValues(alpha: 0)),
         ),
+        child: Icon(Icons.person_outline, size: 24, color: colorScheme.outline),
       ),
     );
   }
 
   Widget _buildFormCard() {
+    final colorScheme = Theme.of(context).colorScheme;
     return Container(
       padding: const EdgeInsets.all(14),
       decoration: BoxDecoration(
-        color: AppColors.white,
+        color: colorScheme.surface,
         borderRadius: BorderRadius.circular(16),
-        border: Border.all(color: AppColors.messageCardBorder),
+        border: Border.all(color: colorScheme.outlineVariant),
       ),
       child: Column(
         children: [
@@ -149,12 +149,13 @@ class _AddContactScreenState extends State<AddContactScreen> {
   }
 
   Widget _buildDeleteRow() {
+    final colorScheme = Theme.of(context).colorScheme;
     return Padding(
       padding: const EdgeInsets.only(bottom: AppSpacing.sm),
       child: LinkButton(
         text: context.l10n.contactDelete,
         onTap: _handleDelete,
-        foregroundColor: AppColors.red600,
+        foregroundColor: colorScheme.error,
       ),
     );
   }
@@ -177,6 +178,7 @@ class _AddContactScreenState extends State<AddContactScreen> {
   }
 
   void _handleDelete() {
+    final colorScheme = Theme.of(context).colorScheme;
     showDialog(
       context: context,
       builder: (context) => AlertDialog(
@@ -195,7 +197,7 @@ class _AddContactScreenState extends State<AddContactScreen> {
             },
             child: Text(
               context.l10n.commonDelete,
-              style: const TextStyle(color: AppColors.red600),
+              style: TextStyle(color: colorScheme.error),
             ),
           ),
         ],