refactor(structure): reorganize app layout

BREAKING CHANGE: root backend/frontend directories and old run/manage entrypoints were removed. Use apps/backend, apps/frontend, and python main.py commands instead.

apps/backend/utils/db_helpers.py

@@ -0,0 +1,123 @@
+"""
+数据库操作辅助函数
+
+提供统一的资源查询、权限验证等通用功能
+"""
+from typing import TypeVar, Type, Optional, Any
+from sqlalchemy.orm import Session
+from fastapi import HTTPException, status
+
+T = TypeVar('T')
+
+
+def get_or_404(
+    model: Type[T],
+    model_id: int,
+    db: Session,
+    error_message: Optional[str] = None
+) -> T:
+    """
+    查询资源，不存在则抛出 404
+
+    Args:
+        model: SQLAlchemy 模型类
+        model_id: 资源 ID
+        db: 数据库会话
+        error_message: 自定义错误消息
+
+    Returns:
+        查询到的资源对象
+
+    Raises:
+        HTTPException: 404 资源不存在
+    """
+    obj = db.query(model).filter(model.id == model_id).first()
+    if not obj:
+        default_message = f"{model.__name__}不存在"
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=error_message or default_message
+        )
+    return obj
+
+
+def get_owned_or_403(
+    model: Type[T],
+    model_id: int,
+    user_id: int,
+    db: Session,
+    error_message: Optional[str] = None
+) -> T:
+    """
+    查询资源并验证归属，否则抛出 403
+
+    Args:
+        model: SQLAlchemy 模型类（必须有 user_id 字段）
+        model_id: 资源 ID
+        user_id: 当前用户 ID
+        db: 数据库会话
+        error_message: 自定义错误消息
+
+    Returns:
+        查询到的资源对象
+
+    Raises:
+        HTTPException: 403 无权访问此资源
+    """
+    obj = db.query(model).filter(
+        model.id == model_id,
+        model.user_id == user_id
+    ).first()
+
+    if not obj:
+        # 先检查资源是否存在
+        exists = db.query(model).filter(model.id == model_id).first()
+        if not exists:
+            raise HTTPException(
+                status_code=status.HTTP_404_NOT_FOUND,
+                detail=f"{model.__name__}不存在"
+            )
+        # 资源存在但不属于当前用户
+        default_message = f"无权访问此{model.__name__}"
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail=error_message or default_message
+        )
+
+    return obj
+
+
+def get_by_field_or_404(
+    model: Type[T],
+    field_name: str,
+    field_value: Any,
+    db: Session,
+    error_message: Optional[str] = None
+) -> T:
+    """
+    根据字段查询资源，不存在则抛出 404
+
+    Args:
+        model: SQLAlchemy 模型类
+        field_name: 字段名
+        field_value: 字段值
+        db: 数据库会话
+        error_message: 自定义错误消息
+
+    Returns:
+        查询到的资源对象
+
+    Raises:
+        HTTPException: 404 资源不存在
+    """
+    obj = db.query(model).filter(
+        getattr(model, field_name) == field_value
+    ).first()
+
+    if not obj:
+        default_message = f"{model.__name__}不存在"
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail=error_message or default_message
+        )
+    return obj