feat(app): 共享 UI 组件 + 4 个关键 UX bug 修复

Phase 0 — 共享组件:
- EmptyStateWidget: 统一空状态 (icon + title + subtitle + CTA)
- ErrorStateWidget: 统一错误状态 (message + retry)
- SkeletonBox + SkeletonList: 统一骨架屏加载 (shimmer 动画)

Phase 1 — Bug 修复:
- 班级评论按 journalId 过滤，避免显示在错误日记卡片下
- moodCellColors key 修正: love/tired → angry/thinking
- 日历非 CalendarLoaded 状态改为加载指示器 (不再 SizedBox.shrink)
- 贴纸数统计改为 '--' 占位 (之前错误显示日记总数)

app/lib/core/theme/app_colors.dart

@@ -177,12 +177,13 @@ class AppColors {
   };
 
   /// 心情 → 日历单元格背景色
+  /// key 必须与 Mood 枚举值一致: happy/calm/sad/angry/thinking
   static const Map<String, Color> moodCellColors = {
-    'happy': secondarySoftLight, // #D4E8DC
-    'love': roseSoftLight,       // #F0DADA
-    'calm': tertiarySoftLight,   // #FBE8C8
-    'sad': Color(0xFFD4DDE8),    // 灰蓝
-    'tired': Color(0xFFE8E4E0),  // 灰棕
+    'happy': secondarySoftLight, // 😊 开心 — 鼠尾草绿 #D4E8DC
+    'calm': tertiarySoftLight,   // 😌 平静 — 暖金 #FBE8C8
+    'sad': Color(0xFFD4DDE8),    // 😢 难过 — 灰蓝
+    'angry': Color(0xFFFFE0D6),  // 😠 生气 — 暖珊瑚 (与 primaryContainer 一致)
+    'thinking': Color(0xFFE8E4E0), // 🤔 思考 — 灰棕
   };
 
   // ===== 浅色主题色彩方案 =====

app/lib/features/calendar/views/calendar_page.dart

@@ -59,7 +59,9 @@ class _CalendarView extends StatelessWidget {
           );
         }
 
-        if (state is! CalendarLoaded) return const SizedBox.shrink();
+        if (state is! CalendarLoaded) {
+          return const Center(child: CircularProgressIndicator());
+        }
         final loaded = state;
 
         return Column(

app/lib/features/class_/views/class_page.dart

@@ -344,31 +344,35 @@ class _DiaryWallCard extends StatelessWidget {
                   color: colorScheme.onSurface.withValues(alpha: 0.4),
                 ),
               ),
-              // 评语
-              if (comments.isNotEmpty) ...[
-                const SizedBox(height: 8),
-                Container(
-                  padding: const EdgeInsets.all(8),
-                  decoration: BoxDecoration(
-                    color: colorScheme.primaryContainer.withValues(alpha: 0.3),
-                    borderRadius: AppRadius.smBorder,
-                  ),
-                  child: Row(
-                    children: [
-                      const Icon(Icons.rate_review_rounded, size: 14),
-                      const SizedBox(width: 4),
-                      Expanded(
-                        child: Text(
-                          comments.first.content,
-                          style: theme.textTheme.bodySmall,
-                          maxLines: 2,
-                          overflow: TextOverflow.ellipsis,
+              // 评语（按 journalId 过滤，避免显示在错误卡片下）
+              ...(() {
+                final journalComments = comments.where((c) => c.journalId == journal.id).toList();
+                if (journalComments.isEmpty) return <Widget>[];
+                return [
+                  const SizedBox(height: 8),
+                  Container(
+                    padding: const EdgeInsets.all(8),
+                    decoration: BoxDecoration(
+                      color: colorScheme.primaryContainer.withValues(alpha: 0.3),
+                      borderRadius: AppRadius.smBorder,
+                    ),
+                    child: Row(
+                      children: [
+                        const Icon(Icons.rate_review_rounded, size: 14),
+                        const SizedBox(width: 4),
+                        Expanded(
+                          child: Text(
+                            journalComments.first.content,
+                            style: theme.textTheme.bodySmall,
+                            maxLines: 2,
+                            overflow: TextOverflow.ellipsis,
+                          ),
                         ),
-                      ),
-                    ],
+                      ],
+                    ),
                   ),
-                ),
-              ],
+                ];
+              })(),
               // 写评语按钮（仅老师可见）
               if (_isTeacher(context)) ...[
                 const SizedBox(height: 8),

app/lib/features/profile/views/profile_page.dart

@@ -425,7 +425,7 @@ class _LiveStatsBarState extends State<_LiveStatsBar> {
           VerticalDivider(width: 1, indent: 4, endIndent: 4, color: widget.borderSoft),
           _StatItem(label: '本月日记', value: '$_monthCount', valueColor: widget.colorScheme.onSurface),
           VerticalDivider(width: 1, indent: 4, endIndent: 4, color: widget.borderSoft),
-          _StatItem(label: '贴纸数', value: _totalCount > 0 ? '$_totalCount' : '0', valueColor: widget.colorScheme.onSurface),
+          _StatItem(label: '贴纸数', value: '--', valueColor: widget.colorScheme.onSurface),
         ],
       ),
     );

app/lib/widgets/empty_state_widget.dart

@@ -0,0 +1,95 @@
+// 共享空状态组件 — 统一所有页面的空数据展示
+//
+// 使用: EmptyStateWidget(icon: Icons.xxx, title: '暂无数据', subtitle: '下拉刷新试试')
+// 样式参考: home_page._EmptyJournalState — 大图标淡化 + 标题 + 副标题 + 暖色按钮
+
+import 'package:flutter/material.dart';
+
+import '../core/constants/design_tokens.dart';
+import '../core/theme/app_colors.dart';
+import '../core/theme/app_radius.dart';
+
+/// 统一空状态组件 — 图标 + 标题 + 可选副标题 + 可选操作按钮
+class EmptyStateWidget extends StatelessWidget {
+  const EmptyStateWidget({
+    super.key,
+    required this.icon,
+    required this.title,
+    this.subtitle,
+    this.actionLabel,
+    this.onAction,
+    this.iconSize = 64,
+  });
+
+  /// 主图标
+  final IconData icon;
+
+  /// 图标大小
+  final double iconSize;
+
+  /// 标题文字
+  final String title;
+
+  /// 副标题（灰色小字）
+  final String? subtitle;
+
+  /// 操作按钮文字（不传则不显示按钮）
+  final String? actionLabel;
+
+  /// 操作按钮回调
+  final VoidCallback? onAction;
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return Center(
+      child: Padding(
+        padding: const EdgeInsets.symmetric(vertical: DesignTokens.spacing40),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            Icon(
+              icon,
+              size: iconSize,
+              color: theme.colorScheme.onSurface.withValues(alpha: 0.2),
+            ),
+            const SizedBox(height: DesignTokens.spacing16),
+            Text(
+              title,
+              style: theme.textTheme.bodyLarge?.copyWith(
+                color: theme.colorScheme.onSurfaceVariant,
+              ),
+              textAlign: TextAlign.center,
+            ),
+            if (subtitle != null) ...[
+              const SizedBox(height: DesignTokens.spacing8),
+              Text(
+                subtitle!,
+                style: theme.textTheme.bodyMedium?.copyWith(
+                  color: theme.colorScheme.onSurfaceVariant.withValues(alpha: 0.6),
+                ),
+                textAlign: TextAlign.center,
+              ),
+            ],
+            if (actionLabel != null && onAction != null) ...[
+              const SizedBox(height: DesignTokens.spacing24),
+              FilledButton.icon(
+                onPressed: onAction,
+                icon: const Icon(Icons.add_rounded),
+                label: Text(actionLabel!),
+                style: FilledButton.styleFrom(
+                  backgroundColor: AppColors.accent,
+                  foregroundColor: AppColors.bgLight,
+                  shape: RoundedRectangleBorder(
+                    borderRadius: AppRadius.pillBorder,
+                  ),
+                  padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 12),
+                ),
+              ),
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+}

app/lib/widgets/error_state_widget.dart

@@ -0,0 +1,72 @@
+// 共享错误状态组件 — 统一所有页面的错误展示
+//
+// 使用: ErrorStateWidget(message: '加载失败', onRetry: () => ...)
+// 样式: 云朵图标 + 错误信息 + 重试按钮
+
+import 'package:flutter/material.dart';
+
+import '../core/constants/design_tokens.dart';
+import '../core/theme/app_radius.dart';
+
+/// 统一错误状态组件 — 图标 + 错误信息 + 可选重试按钮
+class ErrorStateWidget extends StatelessWidget {
+  const ErrorStateWidget({
+    super.key,
+    required this.message,
+    this.onRetry,
+    this.icon = Icons.cloud_off_rounded,
+  });
+
+  /// 错误描述文字
+  final String message;
+
+  /// 重试回调（不传则不显示重试按钮）
+  final VoidCallback? onRetry;
+
+  /// 主图标（默认云朵离线图标）
+  final IconData icon;
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return Center(
+      child: Padding(
+        padding: const EdgeInsets.symmetric(
+          horizontal: DesignTokens.spacing24,
+          vertical: DesignTokens.spacing40,
+        ),
+        child: Column(
+          mainAxisSize: MainAxisSize.min,
+          children: [
+            Icon(
+              icon,
+              size: 56,
+              color: theme.colorScheme.onSurface.withValues(alpha: 0.25),
+            ),
+            const SizedBox(height: DesignTokens.spacing16),
+            Text(
+              message,
+              style: theme.textTheme.bodyMedium?.copyWith(
+                color: theme.colorScheme.onSurfaceVariant,
+              ),
+              textAlign: TextAlign.center,
+            ),
+            if (onRetry != null) ...[
+              const SizedBox(height: DesignTokens.spacing20),
+              TextButton.icon(
+                onPressed: onRetry,
+                icon: const Icon(Icons.refresh_rounded, size: 18),
+                label: const Text('重试'),
+                style: TextButton.styleFrom(
+                  shape: RoundedRectangleBorder(
+                    borderRadius: AppRadius.pillBorder,
+                  ),
+                ),
+              ),
+            ],
+          ],
+        ),
+      ),
+    );
+  }
+}

app/lib/widgets/skeleton_loading.dart

@@ -0,0 +1,156 @@
+// 共享骨架屏加载组件 — 替代 CircularProgressIndicator
+//
+// 使用: SkeletonBox(height: 80) 或 SkeletonBox(height: 48, shimmer: true)
+// 样式: 灰色圆角矩形 + 可选 shimmer 微光动画
+
+import 'package:flutter/material.dart';
+
+import '../core/theme/app_radius.dart';
+
+/// 骨架屏加载占位块
+class SkeletonBox extends StatelessWidget {
+  const SkeletonBox({
+    super.key,
+    required this.height,
+    this.width,
+    this.shimmer = false,
+    this.borderRadius,
+  });
+
+  /// 高度
+  final double height;
+
+  /// 宽度（默认撑满父容器）
+  final double? width;
+
+  /// 是否启用 shimmer 微光动画
+  final bool shimmer;
+
+  /// 自定义圆角（默认 AppRadius.md）
+  final BorderRadius? borderRadius;
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    final bgColor = theme.colorScheme.surfaceContainerHighest.withValues(alpha: 0.3);
+    final radius = borderRadius ?? AppRadius.mdBorder;
+
+    if (shimmer) {
+      return _ShimmerBox(
+        height: height,
+        width: width,
+        bgColor: bgColor,
+        borderRadius: radius,
+      );
+    }
+
+    return Container(
+      height: height,
+      width: width,
+      decoration: BoxDecoration(
+        color: bgColor,
+        borderRadius: radius,
+      ),
+    );
+  }
+}
+
+/// 带微光动画的骨架屏
+class _ShimmerBox extends StatefulWidget {
+  const _ShimmerBox({
+    required this.height,
+    this.width,
+    required this.bgColor,
+    required this.borderRadius,
+  });
+
+  final double height;
+  final double? width;
+  final Color bgColor;
+  final BorderRadius borderRadius;
+
+  @override
+  State<_ShimmerBox> createState() => _ShimmerBoxState();
+}
+
+class _ShimmerBoxState extends State<_ShimmerBox>
+    with SingleTickerProviderStateMixin {
+  late final AnimationController _controller;
+
+  @override
+  void initState() {
+    super.initState();
+    _controller = AnimationController(
+      vsync: this,
+      duration: const Duration(milliseconds: 1500),
+    )..repeat();
+  }
+
+  @override
+  void dispose() {
+    _controller.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final theme = Theme.of(context);
+    return AnimatedBuilder(
+      animation: _controller,
+      builder: (context, child) {
+        return Container(
+          height: widget.height,
+          width: widget.width,
+          decoration: BoxDecoration(
+            borderRadius: widget.borderRadius,
+            gradient: LinearGradient(
+              begin: Alignment(-1.0 + 2.0 * _controller.value, 0),
+              end: Alignment(1.0 + 2.0 * _controller.value, 0),
+              colors: [
+                widget.bgColor,
+                theme.colorScheme.surfaceContainerHighest.withValues(alpha: 0.15),
+                widget.bgColor,
+              ],
+            ),
+          ),
+        );
+      },
+    );
+  }
+}
+
+/// 通用列表骨架屏 — 显示 N 行占位
+class SkeletonList extends StatelessWidget {
+  const SkeletonList({
+    super.key,
+    this.itemCount = 5,
+    this.itemHeight = 72,
+    this.spacing = 12,
+    this.shimmer = false,
+  });
+
+  /// 骨架行数
+  final int itemCount;
+
+  /// 每行高度
+  final double itemHeight;
+
+  /// 行间距
+  final double spacing;
+
+  /// 是否 shimmer
+  final bool shimmer;
+
+  @override
+  Widget build(BuildContext context) {
+    return ListView.builder(
+      physics: const NeverScrollableScrollPhysics(),
+      shrinkWrap: true,
+      itemCount: itemCount,
+      itemBuilder: (_, _) => Padding(
+        padding: EdgeInsets.only(bottom: spacing),
+        child: SkeletonBox(height: itemHeight, shimmer: shimmer),
+      ),
+    );
+  }
+}