refactor(backend): 重构后端异常处理和模型管理

- 新增自定义异常类 BizException、NoteError 和 ProviderError
- 优化了模型管理相关的逻辑，包括加载、删除和测试连接等功能
- 改进了 Douyin 下载器的错误处理
- 调整了任务重试逻辑和笔记生成的异常处理- 更新了相关组件和页面以适应新的异常处理机制

backend/app/exceptions/biz_exception.py

@@ -0,0 +1,6 @@
+# exceptions/biz_exception.py
+
+class BizException(Exception):
+    def __init__(self, code: int, message: str = "业务异常"):
+        self.code = code
+        self.message = message

backend/app/exceptions/exception_handlers.py

@@ -0,0 +1,33 @@
+# middlewares/exception_handler.py
+
+from fastapi import Request
+from fastapi import FastAPI
+
+from app.enmus.exception import NoteErrorEnum
+from app.exceptions.biz_exception import BizException
+from app.exceptions.note import NoteError
+from app.exceptions.provider import ProviderError
+from app.utils.logger import get_logger
+from app.utils.response import ResponseWrapper as R
+import traceback
+
+logger = get_logger(__name__)
+
+def register_exception_handlers(app: FastAPI):
+    @app.exception_handler(BizException)
+    async def biz_exception_handler(request: Request, exc: BizException):
+        logger.error(f"BizException: {exc.code} - {exc.message}")
+        return R.error(code=exc.code, msg=str(exc.message))
+    @app.exception_handler(NoteError)
+    async def note_exception_handler(request: Request, exc: NoteError):
+        logger.error(f"NoteError: {exc.code} - {exc.message}")
+        return R.error(code=exc.code, msg=str(exc.message))
+    @app.exception_handler(ProviderError)
+    async def provider_exception_handler(request: Request, exc: ProviderError):
+        logger.error(f"供应商模块错误: {exc.code} - {exc.message}")
+        return R.error(code=exc.code, msg=str(exc.message))
+
+    @app.exception_handler(Exception)
+    async def general_exception_handler(request: Request, exc: Exception):
+        logger.error(f"系统异常: {str(exc)}\n{traceback.format_exc()}")
+        return R.error(code=500000, msg="系统异常")

backend/app/exceptions/note.py

@@ -0,0 +1,9 @@
+# exceptions.py
+from app.enmus.exception import ProviderErrorEnum
+
+
+class NoteError(Exception):
+    def __init__(self, message: str,code: ProviderErrorEnum) -> None:
+        super().__init__(message)
+        self.code=code
+        self.message = message

backend/app/exceptions/provider.py

@@ -1,5 +1,12 @@
 # exceptions.py
-class ConnectionTestError(Exception):
-    def __init__(self, message: str):
+from app.enmus.exception import ProviderErrorEnum
+
+
+class ProviderError(Exception):
+    def __init__(self, message: str,code: ProviderErrorEnum) -> None:
         super().__init__(message)
-        self.message = message
+        self.code=code
+        self.message = message
+        
+        
+