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/tests/conftest.py

@@ -5,21 +5,22 @@ from app.database import Base, get_db
 from app.main import app
 from httpx import AsyncClient
 
-TEST_DATABASE_URL = "sqlite+aiosqlite:///./test.db"
+TEST_DATABASE_URL = "sqlite+aiosqlite:///:memory:"
 
 @pytest_asyncio.fixture
 async def db():
     engine = create_async_engine(TEST_DATABASE_URL, echo=False)
-    async with engine.begin() as conn:
-        await conn.run_sync(Base.metadata.create_all)
-    
-    async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
-    async with async_session() as session:
-        yield session
-    
-    async with engine.begin() as conn:
-        await conn.run_sync(Base.metadata.drop_all)
-    await engine.dispose()
+    try:
+        async with engine.begin() as conn:
+            await conn.run_sync(Base.metadata.create_all)
+        
+        async_session = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
+        async with async_session() as session:
+            yield session
+    finally:
+        async with engine.begin() as conn:
+            await conn.run_sync(Base.metadata.drop_all)
+        await engine.dispose()
 
 @pytest_asyncio.fixture
 async def client(db):