feat(backend): 添加核心架构模块

- 添加认证模块 (auth.py)
- 添加 CRUD 基础操作 (crud.py)
- 添加异常处理 (exceptions.py)
- 添加日志模块 (logging.py)
- 添加响应格式 (response.py)
- 添加依赖注入 (dependencies.py)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/core/exceptions.py

@@ -0,0 +1,119 @@
+"""
+Custom Exceptions
+自定义异常类
+"""
+from typing import Any, Optional
+
+
+class AppException(Exception):
+    """基础应用异常"""
+
+    def __init__(
+        self,
+        message: str,
+        code: str = "INTERNAL_ERROR",
+        status_code: int = 500,
+        details: Optional[dict] = None
+    ):
+        self.message = message
+        self.code = code
+        self.status_code = status_code
+        self.details = details
+        super().__init__(self.message)
+
+
+class NotFoundException(AppException):
+    """资源未找到异常"""
+
+    def __init__(self, resource: str, resource_id: Any = None):
+        message = f"{resource} not found"
+        if resource_id:
+            message = f"{resource} with id '{resource_id}' not found"
+        super().__init__(
+            message=message,
+            code="NOT_FOUND",
+            status_code=404
+        )
+
+
+class ValidationException(AppException):
+    """验证异常"""
+
+    def __init__(self, message: str, field: str = None, details: dict = None):
+        super().__init__(
+            message=message,
+            code="VALIDATION_ERROR",
+            status_code=422,
+            details={"field": field, **(details or {})}
+        )
+
+
+class DuplicateException(AppException):
+    """重复资源异常"""
+
+    def __init__(self, resource: str, field: str = None):
+        message = f"{resource} already exists"
+        if field:
+            message = f"{resource} with {field} already exists"
+        super().__init__(
+            message=message,
+            code="DUPLICATE",
+            status_code=409
+        )
+
+
+class UnauthorizedException(AppException):
+    """未授权异常"""
+
+    def __init__(self, message: str = "Unauthorized"):
+        super().__init__(
+            message=message,
+            code="UNAUTHORIZED",
+            status_code=401
+        )
+
+
+class ForbiddenException(AppException):
+    """禁止访问异常"""
+
+    def __init__(self, message: str = "Forbidden"):
+        super().__init__(
+            message=message,
+            code="FORBIDDEN",
+            status_code=403
+        )
+
+
+class RateLimitException(AppException):
+    """速率限制异常"""
+
+    def __init__(self, message: str = "Rate limit exceeded"):
+        super().__init__(
+            message=message,
+            code="RATE_LIMIT",
+            status_code=429
+        )
+
+
+class FileProcessingException(AppException):
+    """文件处理异常"""
+
+    def __init__(self, message: str, file_name: str = None):
+        details = {"file_name": file_name} if file_name else None
+        super().__init__(
+            message=message,
+            code="FILE_PROCESSING_ERROR",
+            status_code=422,
+            details=details
+        )
+
+
+class DatabaseException(AppException):
+    """数据库异常"""
+
+    def __init__(self, message: str = "Database operation failed"):
+        super().__init__(
+            message=message,
+            code="DATABASE_ERROR",
+            status_code=500
+        )