fix: all lint errors, test + lint pre-commit passing

Frontend:
- Split nodeTypes/edgeTypes into separate .ts files (react-refresh)
- Remove setState-in-effect in NodeModal (key prop reset)
- Fix handleSave accessed before declaration (useRef pattern)
- Exclude src/components/ui/** from eslint (shadcn generated)
- Use defineConfig from vitest/config for test type support

Backend:
- ruff --fix: sort imports, datetime.UTC alias
- Raise line-length to 120, ignore E501 in tests
- Break long update_node/update_edge signatures
- pyproject.toml: per-file-ignores for tests

backend/tests/conftest.py

@@ -0,0 +1,39 @@
+import pytest
+from httpx import ASGITransport, AsyncClient
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
+
+from app.db.database import Base, get_db
+from app.main import app
+
+TEST_DB_URL = "sqlite+aiosqlite:///:memory:"
+
+
+@pytest.fixture
+async def db_session():
+    engine = create_async_engine(TEST_DB_URL)
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+    session_factory = async_sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
+    async with session_factory() as session:
+        yield session
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.drop_all)
+    await engine.dispose()
+
+
+@pytest.fixture
+async def client(db_session: AsyncSession):
+    app.dependency_overrides[get_db] = lambda: db_session
+    async with AsyncClient(transport=ASGITransport(app=app), base_url="http://test") as c:
+        yield c
+    app.dependency_overrides.clear()
+
+
+@pytest.fixture
+def auth_headers(client):
+    """Returns a coroutine that logs in and returns auth headers."""
+    async def _get():
+        res = await client.post("/api/v1/auth/login", json={"username": "admin", "password": "admin"})
+        token = res.json()["access_token"]
+        return {"Authorization": f"Bearer {token}"}
+    return _get