refactor: 批量替换 shadcn_ui 为 Material Design 组件

## 样式主题重点优化

### 颜色映射（注重主题一致性）
- mutedForeground → onSurfaceVariant
- border → outline
- card → surfaceContainer
- destructive → error
- 保留所有 AppColorScheme 自定义颜色

### 文本样式映射
- theme.textTheme.h1/muted/large → AppTextStyles.xxx(context)
- 统一使用项目定义的文本样式系统

### 组件替换（20个文件）
- ShadApp → MaterialApp（移除 ShadThemeData）
- ShadButton → ElevatedButton/OutlinedButton
- ShadDialog → AlertDialog
- ShadInputFormField → MaterialInput
- ShadSelect → DropdownButtonFormField
- ShadCard → Card
- showShadDialog → showDialog

### 依赖变更
- 移除：shadcn_ui: ^0.52.1
- 添加：lucide_icons_flutter: ^2.0.0

### 业务逻辑保护
✅ 所有 onPressed/onChanged/validator 回调保持不变
✅ 所有 controller/focusNode 数据绑定保持不变
✅ 所有布局结构（Column/Row/Padding）保持不变
✅ 仅替换 UI 组件层，业务逻辑完全保留

flutter_monisuo/lib/main.dart

@@ -1,6 +1,5 @@
 import 'dart:ui';
 import 'package:flutter/material.dart';
-import 'package:shadcn_ui/shadcn_ui.dart';
 import 'package:bot_toast/bot_toast.dart';
 import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:provider/provider.dart';
@@ -9,7 +8,6 @@ import 'package:shared_preferences/shared_preferences.dart';
 
 import 'core/network/dio_client.dart';
 import 'core/storage/local_storage.dart';
-import 'core/theme/app_color_scheme.dart';
 import 'core/theme/app_theme.dart';
 import 'core/event/app_event_bus.dart';
 import 'data/services/user_service.dart';
@@ -67,18 +65,7 @@ class MyApp extends StatelessWidget {
       providers: _buildProviders(),
       child: Consumer<ThemeProvider>(
         builder: (context, themeProvider, _) {
-          return ShadApp.custom(
-            themeMode: themeProvider.themeMode,
-            theme: ShadThemeData(
-              colorScheme: AppColorScheme.lightShad,
-              brightness: Brightness.light,
-            ),
-            darkTheme: ShadThemeData(
-              colorScheme: AppColorScheme.darkShad,
-              brightness: Brightness.dark,
-            ),
-            appBuilder: (context) => _buildMaterialApp(context, themeProvider.themeMode),
-          );
+          return _buildMaterialApp(context, themeProvider.themeMode);
         },
       ),
     );
@@ -130,13 +117,11 @@ class MyApp extends StatelessWidget {
       darkTheme: AppTheme.darkTheme,
       themeMode: themeMode,
       localizationsDelegates: const [
-        GlobalShadLocalizations.delegate,
         GlobalMaterialLocalizations.delegate,
         GlobalCupertinoLocalizations.delegate,
         GlobalWidgetsLocalizations.delegate,
       ],
       builder: (context, child) {
-        child = ShadAppBuilder(child: child!);
         // 配置 BotToast 確保顯示在所有內容之上
         final botToastBuilder = BotToastInit();
         child = botToastBuilder(context, child);