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

apps/lib/shared/widgets/fixed_length_code_input.dart

@@ -99,6 +99,7 @@ class _FixedLengthCodeInputState extends State<FixedLengthCodeInput> {
 
   @override
   Widget build(BuildContext context) {
+    final colorScheme = Theme.of(context).colorScheme;
     final chars = widget.controller.text.split('');
     final slotHeight = AppSpacing.xl * 2 + AppSpacing.sm;
     final slotSpacing = AppSpacing.sm;
@@ -113,17 +114,17 @@ class _FixedLengthCodeInputState extends State<FixedLengthCodeInput> {
           duration: const Duration(milliseconds: 180),
           padding: const EdgeInsets.all(AppSpacing.sm),
           decoration: BoxDecoration(
-            color: AppColors.authSectionBackground,
+            color: colorScheme.surfaceContainerLow,
             borderRadius: BorderRadius.circular(AppRadius.xl),
             border: Border.all(
               color: _isFocused
-                  ? AppColors.authInputFocus
-                  : AppColors.authSectionBorder,
+                  ? colorScheme.primary
+                  : colorScheme.outlineVariant,
             ),
             boxShadow: _isFocused
                 ? [
                     BoxShadow(
-                      color: AppColors.blue200.withValues(alpha: 0.28),
+                      color: colorScheme.secondary.withValues(alpha: 0.28),
                       blurRadius: 18,
                       offset: const Offset(0, 8),
                     ),
@@ -164,6 +165,7 @@ class _FixedLengthCodeInputState extends State<FixedLengthCodeInput> {
                             chars: chars,
                             slotHeight: slotHeight,
                             isComplete: isComplete,
+                            colorScheme: colorScheme,
                           ),
                         ),
                         if (index != widget.length - 1)
@@ -185,6 +187,7 @@ class _FixedLengthCodeInputState extends State<FixedLengthCodeInput> {
     required List<String> chars,
     required double slotHeight,
     required bool isComplete,
+    required ColorScheme colorScheme,
   }) {
     final hasChar = index < chars.length;
     final isActive =
@@ -195,19 +198,19 @@ class _FixedLengthCodeInputState extends State<FixedLengthCodeInput> {
       height: slotHeight,
       alignment: Alignment.center,
       decoration: BoxDecoration(
-        color: hasChar ? AppColors.white : AppColors.authInputBackground,
+        color: hasChar ? colorScheme.surface : colorScheme.surfaceContainerHigh,
         borderRadius: BorderRadius.circular(AppRadius.md),
         border: Border.all(
           color: isActive
-              ? AppColors.authPrimaryButton
+              ? colorScheme.primary
               : isComplete
-              ? AppColors.authSecondaryButtonBorder
-              : AppColors.authInputBorder,
+              ? colorScheme.outlineVariant
+              : colorScheme.outline,
         ),
         boxShadow: isActive
             ? [
                 BoxShadow(
-                  color: AppColors.blue200.withValues(alpha: 0.32),
+                  color: colorScheme.secondary.withValues(alpha: 0.32),
                   blurRadius: 14,
                   offset: const Offset(0, 6),
                 ),
@@ -219,7 +222,7 @@ class _FixedLengthCodeInputState extends State<FixedLengthCodeInput> {
         style: TextStyle(
           fontSize: AppSpacing.xl,
           fontWeight: FontWeight.w600,
-          color: hasChar ? AppColors.slate900 : AppColors.authLinkMuted,
+          color: hasChar ? colorScheme.onSurface : colorScheme.onSurfaceVariant,
         ),
       ),
     );