feat: Implement file download token management and restructure file routes

- Added DownloadTokenManager for creating and verifying JWT download tokens.
- Introduced new download routes for creating download tokens and downloading files using tokens.
- Restructured file upload routes into a dedicated sub-router.
- Updated file upload session management with improved error handling and response structures.
- Created a new MCP (Microservice Communication Protocol) router with basic request and response models.
- Added base models for MCP requests and responses, including method enumeration.

models/setting.py

@@ -40,6 +40,32 @@ class SiteConfigResponse(SQLModelBase):
     """验证码密钥"""
 
 
+# ==================== 管理员设置 DTO ====================
+
+class SettingItem(SQLModelBase):
+    """设置项 DTO"""
+
+    name: str
+    """设置项名称"""
+
+    value: str | None = None
+    """设置值"""
+
+
+class SettingsUpdateRequest(SQLModelBase):
+    """更新设置请求 DTO"""
+
+    settings: dict[str, dict[str, str | None]]
+    """按类型分组的设置项，格式: {"basic": {"siteName": "xxx", ...}, ...}"""
+
+
+class SettingsGetResponse(SQLModelBase):
+    """获取设置响应 DTO"""
+
+    settings: dict[str, dict[str, str | None]] = {}
+    """按类型分组的设置项"""
+
+
 # ==================== 数据库模型 ====================
 
 class SettingsType(StrEnum):