fix(app): 修复 P2~P4 共 10 项前端问题

P2 必须修复:
- 教师布置主题 classId 从硬编码改为班级下拉选择器
- 班级日记墙使用服务端 classId 过滤替代前端过滤
- Profile 统计栏接入 JournalRepository 真实数据
- WeeklyPage 从全硬编码改为 JournalRepository 数据驱动

P3 建议改进:
- 提取 mood_utils.dart 公共函数，消除 4 处重复定义
- 贴纸库搜索框连接 StickerBloc 按名称过滤

P4 细节打磨:
- 家长页多孩子时显示 DropdownButton 选择器
- 搜索结果日记卡片点击跳转 /editor?id=
- MonthlyPage 照片数量从 JournalElement 统计
- calendar_page/mood_page/search_page 统一使用 moodToEmoji/moodToLabel

app/lib/features/teacher/views/teacher_page.dart

@@ -7,6 +7,7 @@ import 'package:nuanji_app/core/theme/app_colors.dart';
 import 'package:nuanji_app/core/theme/app_radius.dart';
 import 'package:nuanji_app/data/repositories/class_repository.dart';
 import 'package:nuanji_app/data/repositories/journal_repository.dart';
+import 'package:nuanji_app/data/models/school_class.dart';
 import '../../class_/bloc/class_bloc.dart';
 
 /// 老师管理页面 — 教师专属功能入口
@@ -162,57 +163,91 @@ class _TeacherView extends StatelessWidget {
     final titleController = TextEditingController();
     final descController = TextEditingController();
 
+    // 从 ClassBloc 获取已加载的班级列表
+    final classState = context.read<ClassBloc>().state;
+    final classes = classState is ClassListLoaded ? classState.classes : <SchoolClass>[];
+
+    // 无班级时提示先创建
+    if (classes.isEmpty) {
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('请先创建班级后再布置主题')),
+      );
+      return;
+    }
+
+    String selectedClassId = classes.first.id;
+
     showDialog(
       context: context,
-      builder: (dialogContext) => AlertDialog(
-        title: const Text('布置主题'),
-        content: Column(
-          mainAxisSize: MainAxisSize.min,
-          children: [
-            TextField(
-              controller: titleController,
-              decoration: const InputDecoration(
-                labelText: '主题标题',
-                hintText: '例如: 我的周末',
-                border: OutlineInputBorder(),
+      builder: (dialogContext) => StatefulBuilder(
+        builder: (context, setDialogState) => AlertDialog(
+          title: const Text('布置主题'),
+          content: Column(
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              // 班级选择下拉框
+              DropdownButtonFormField<String>(
+                value: selectedClassId,
+                decoration: const InputDecoration(
+                  labelText: '选择班级',
+                  border: OutlineInputBorder(),
+                ),
+                items: classes
+                    .map((c) => DropdownMenuItem(
+                          value: c.id,
+                          child: Text(c.name),
+                        ))
+                    .toList(),
+                onChanged: (v) {
+                  if (v != null) setDialogState(() => selectedClassId = v);
+                },
               ),
+              const SizedBox(height: 12),
+              TextField(
+                controller: titleController,
+                decoration: const InputDecoration(
+                  labelText: '主题标题',
+                  hintText: '例如: 我的周末',
+                  border: OutlineInputBorder(),
+                ),
+              ),
+              const SizedBox(height: 12),
+              TextField(
+                controller: descController,
+                decoration: const InputDecoration(
+                  labelText: '描述（可选）',
+                  hintText: '主题要求和说明',
+                  border: OutlineInputBorder(),
+                ),
+                maxLines: 3,
+              ),
+            ],
+          ),
+          actions: [
+            TextButton(
+              onPressed: () => Navigator.pop(dialogContext),
+              child: const Text('取消'),
             ),
-            const SizedBox(height: 12),
-            TextField(
-              controller: descController,
-              decoration: const InputDecoration(
-                labelText: '描述（可选）',
-                hintText: '主题要求和说明',
-                border: OutlineInputBorder(),
-              ),
-              maxLines: 3,
+            FilledButton(
+              onPressed: () {
+                if (titleController.text.trim().isNotEmpty) {
+                  context.read<ClassBloc>().add(TopicAssign(
+                        classId: selectedClassId,
+                        title: titleController.text.trim(),
+                        description: descController.text.trim().isEmpty
+                            ? null
+                            : descController.text.trim(),
+                      ));
+                  Navigator.pop(dialogContext);
+                  ScaffoldMessenger.of(context).showSnackBar(
+                    const SnackBar(content: Text('主题布置成功！')),
+                  );
+                }
+              },
+              child: const Text('布置'),
             ),
           ],
         ),
-        actions: [
-          TextButton(
-            onPressed: () => Navigator.pop(dialogContext),
-            child: const Text('取消'),
-          ),
-          FilledButton(
-            onPressed: () {
-              if (titleController.text.trim().isNotEmpty) {
-                context.read<ClassBloc>().add(TopicAssign(
-                      classId: 'class-1',
-                      title: titleController.text.trim(),
-                      description: descController.text.trim().isEmpty
-                          ? null
-                          : descController.text.trim(),
-                    ));
-                Navigator.pop(dialogContext);
-                ScaffoldMessenger.of(context).showSnackBar(
-                  const SnackBar(content: Text('主题布置成功！')),
-                );
-              }
-            },
-            child: const Text('布置'),
-          ),
-        ],
       ),
     );
   }