fix:修复项目结构

backend/app/database.py

@@ -0,0 +1,23 @@
+from collections.abc import Generator
+
+from sqlalchemy import create_engine
+from sqlalchemy.orm import declarative_base, sessionmaker
+
+from app.config import settings
+
+settings.data_dir.mkdir(parents=True, exist_ok=True)
+
+engine = create_engine(
+    settings.database_url,
+    connect_args={"check_same_thread": False},
+)
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+Base = declarative_base()
+
+
+def get_db() -> Generator:
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()