feat(school,classes): 实现 P2 长期问题全量改进项

P2-2: 新增 OrgTreeNav 组件（学校→年级→班级三级树形导航，支持搜索过滤/选中高亮/展开折叠）

P2-3: 新增 promoteGradesAction 年级升级功能（中文数字/阿拉伯数字识别，按 order 降序避免冲突）

P2-4: 新增 bulkEnrollStudentsAction（CSV 批量导入学生）+ bulkAssignSubjectTeachersAction（CSV 批量分配教师）

P2-5: 为 department/academicYear/grade 的 9 个 CRUD Action 补充 logAudit 审计日志

同步更新架构图文档 004/005

src/shared/i18n/messages/zh-CN/school.json

@@ -122,7 +122,15 @@
     "optional": "可选",
     "failedCreate": "创建年级失败",
     "failedUpdate": "更新年级失败",
-    "failedDelete": "删除年级失败"
+    "failedDelete": "删除年级失败",
+    "promote": {
+      "title": "年级升级",
+      "description": "将选定学校的所有年级升级一级（如一年级→二年级），保留历史档案。",
+      "confirm": "确认升级",
+      "selectSchool": "请选择学校",
+      "success": "成功升级 {count} 个年级",
+      "failed": "升级失败"
+    }
   },
   "departments": {
     "title": "部门管理",
@@ -205,6 +213,24 @@
   "classManagement": {
     "title": "班级管理",
     "description": "管理班级并分配教师。",
+    "bulk": {
+      "importStudents": {
+        "title": "批量导入学生",
+        "description": "每行一个邮箱，格式：name,email 或仅 email",
+        "placeholder": "张三,zhangsan@example.com\nlisi@example.com",
+        "submit": "导入",
+        "success": "成功导入 {imported} 个学生，{failed} 个失败",
+        "failed": "批量导入失败"
+      },
+      "assignTeachers": {
+        "title": "批量分配教师",
+        "description": "每行格式：班级名称,科目,教师邮箱",
+        "placeholder": "一班,语文,zhangsan@example.com\n二班,数学,lisi@example.com",
+        "submit": "分配",
+        "success": "成功更新 {updated} 个分配，{failed} 个失败",
+        "failed": "批量分配失败"
+      }
+    },
     "grade": {
       "title": "班级管理",
       "description": "管理你所在年级的班级。",
@@ -253,5 +279,12 @@
       "description": "数据加载时发生错误，请重试",
       "retry": "重试"
     }
+  },
+  "orgTree": {
+    "title": "组织架构",
+    "search": "搜索学校/年级/班级...",
+    "empty": "暂无数据",
+    "expandAll": "全部展开",
+    "collapseAll": "全部折叠"
   }
 }