style: apply ruff formatting and move TYPE_CHECKING imports in tests

tests/test_backends.py

@@ -13,13 +13,16 @@ Comprehensive tests covering:
 from __future__ import annotations
 
 import asyncio
-from typing import AsyncGenerator
+from typing import TYPE_CHECKING
 
 import pytest
 
 from fastapi_traffic.backends.memory import MemoryBackend
 from fastapi_traffic.backends.sqlite import SQLiteBackend
 
+if TYPE_CHECKING:
+    from collections.abc import AsyncGenerator
+
 
 @pytest.mark.asyncio
 class TestMemoryBackend:
@@ -163,6 +166,7 @@ class TestMemoryBackendAdvanced:
         """Test concurrent write operations don't corrupt data."""
         backend = MemoryBackend(max_size=1000)
         try:
+
             async def write_key(i: int) -> None:
                 await backend.set(f"key_{i}", {"value": i}, ttl=60.0)
 
@@ -302,6 +306,7 @@ class TestSQLiteBackendAdvanced:
         backend = SQLiteBackend(":memory:")
         await backend.initialize()
         try:
+
             async def write_key(i: int) -> None:
                 await backend.set(f"key_{i}", {"value": i}, ttl=60.0)
 
@@ -377,7 +382,9 @@ class TestBackendInterface:
     """Tests to verify backend interface consistency."""
 
     @pytest.fixture
-    async def backends(self) -> AsyncGenerator[list[MemoryBackend | SQLiteBackend], None]:
+    async def backends(
+        self,
+    ) -> AsyncGenerator[list[MemoryBackend | SQLiteBackend], None]:
         """Create all backend types for testing."""
         memory = MemoryBackend()
         sqlite = SQLiteBackend(":memory:")