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/core/theme/app_color_scheme.dart

@@ -1,5 +1,4 @@
 import 'package:flutter/material.dart';
-import 'package:shadcn_ui/shadcn_ui.dart';
 
 /// Material Design 3 顏色系統 - Pencil Design Theme
 ///
@@ -252,60 +251,6 @@ class AppColorScheme {
     end: Alignment.bottomRight,
   );
 
-  // ============================================
-  // Shadcn ColorScheme - 深色主題
-  // ============================================
-
-  static ShadColorScheme get darkShad => ShadColorScheme(
-    background: darkBackground,
-    foreground: darkOnSurface,
-    card: darkSurfaceContainer,
-    cardForeground: darkOnSurface,
-    popover: darkSurfaceContainerHigh,
-    popoverForeground: darkOnSurface,
-    primary: darkPrimary,
-    primaryForeground: darkOnPrimary,
-    secondary: darkSecondary,
-    secondaryForeground: darkOnSecondary,
-    muted: darkSurfaceContainerHigh,
-    mutedForeground: darkOnSurfaceVariant,
-    accent: darkPrimary.withValues(alpha: 0.15),
-    accentForeground: darkPrimary,
-    destructive: error,
-    destructiveForeground: darkOnSurface,
-    border: darkOutlineVariant.withValues(alpha: 0.15),
-    input: darkOutlineVariant.withValues(alpha: 0.15),
-    ring: darkPrimary,
-    selection: darkPrimary.withValues(alpha: 0.3),
-  );
-
-  // ============================================
-  // Shadcn ColorScheme - 淺色主題
-  // ============================================
-
-  static ShadColorScheme get lightShad => ShadColorScheme(
-    background: lightBackground,
-    foreground: lightOnSurface,
-    card: lightSurfaceLowest,
-    cardForeground: lightOnSurface,
-    popover: lightSurfaceLowest,
-    popoverForeground: lightOnSurface,
-    primary: lightPrimary,
-    primaryForeground: const Color(0xFFFFFFFF),
-    secondary: lightSecondary,
-    secondaryForeground: const Color(0xFFFFFFFF),
-    muted: lightSurfaceHigh,
-    mutedForeground: lightOnSurfaceVariant,
-    accent: lightSecondary.withValues(alpha: 0.1),
-    accentForeground: lightSecondary,
-    destructive: error,
-    destructiveForeground: const Color(0xFFFFFFFF),
-    border: lightOutlineVariant.withValues(alpha: 0.5),
-    input: lightOutlineVariant.withValues(alpha: 0.3),
-    ring: lightSecondary,
-    selection: lightSecondary.withValues(alpha: 0.2),
-  );
-
   // ============================================
   // Material ColorScheme - 深色主題 (Material Design 3)
   // ============================================