refactor: mock清理+安全配置+通用组件+菜单优化

P0安全: SECRET_KEY/ADMIN_PASSWORD/CORS环境变量化, seed仅admin

P1Mock: mock.ts 301->88行, 删8数据mock+5generateMock, net-1300行

P2组件: useToast/useFetchList+ConfirmDialog/FormDialog

P3菜单: menuSections/menuItems->constants/menu.ts

P4API: NotificationsPage/WorkflowPage重写+RolesPage演示

测试: 1050passed, tsc clean

backend/app/schemas/system_setting.py

@@ -0,0 +1,39 @@
+"""系统设置 Schema。"""
+
+from typing import Optional, List
+from pydantic import BaseModel, Field
+
+
+class SettingItem(BaseModel):
+    """单个设置项。"""
+    key: str
+    value: str
+    value_type: str = "string"  # boolean / integer / string
+    group: str = "general"
+    label: str
+    description: Optional[str] = None
+    default_value: Optional[str] = None
+    sort_order: int = 0
+
+    class Config:
+        from_attributes = True
+
+
+class SettingUpdateItem(BaseModel):
+    """单个更新项。"""
+    key: str
+    value: str
+
+
+class SettingBulkUpdate(BaseModel):
+    """批量更新设置项。"""
+    settings: List[SettingUpdateItem] = Field(..., min_length=1)
+
+
+class SettingGroupResponse(BaseModel):
+    """分组设置响应。"""
+    group: str
+    label: str
+    icon: str = ""
+    description: str = ""
+    settings: List[SettingItem]