fix: improve test isolation and configuration

- Use in-memory SQLite for tests to prevent conflicts
- Add try/finally for robust test cleanup
- Make database URL configurable via env var
- Make CORS origins configurable via env var
- Make SQL echo configurable via env var

backend/app/database.py

@@ -1,9 +1,10 @@
+import os
 from sqlalchemy.ext.asyncio import create_async_engine, AsyncSession, async_sessionmaker
 from sqlalchemy.orm import declarative_base
 
-DATABASE_URL = "sqlite+aiosqlite:///./backup_tool.db"
+DATABASE_URL = os.environ.get("DATABASE_URL", "sqlite+aiosqlite:///./backup_tool.db")
 
-engine = create_async_engine(DATABASE_URL, echo=True)
+engine = create_async_engine(DATABASE_URL, echo=os.environ.get("SQL_ECHO", "false").lower() == "true")
 AsyncSessionLocal = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
 
 Base = declarative_base()