fix(llm-gateway): improve type safety and datetime consistency

- Add type annotations for mypy compliance
- Use UTC-aware datetimes consistently (datetime.now(UTC))
- Add type: ignore comments for LiteLLM incomplete stubs
- Fix import ordering and formatting
- Update pyproject.toml mypy configuration

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

mcp-servers/llm-gateway/tests/test_routing.py

@@ -79,14 +79,23 @@ class TestModelRouter:
 
     def test_get_preferred_group_for_agent(self, router: ModelRouter) -> None:
         """Test getting preferred group for agent types."""
-        assert router.get_preferred_group_for_agent("product_owner") == ModelGroup.REASONING
-        assert router.get_preferred_group_for_agent("software_engineer") == ModelGroup.CODE
-        assert router.get_preferred_group_for_agent("devops_engineer") == ModelGroup.FAST
+        assert (
+            router.get_preferred_group_for_agent("product_owner")
+            == ModelGroup.REASONING
+        )
+        assert (
+            router.get_preferred_group_for_agent("software_engineer") == ModelGroup.CODE
+        )
+        assert (
+            router.get_preferred_group_for_agent("devops_engineer") == ModelGroup.FAST
+        )
 
     def test_get_preferred_group_unknown_agent(self, router: ModelRouter) -> None:
         """Test getting preferred group for unknown agent."""
         # Should default to REASONING
-        assert router.get_preferred_group_for_agent("unknown_type") == ModelGroup.REASONING
+        assert (
+            router.get_preferred_group_for_agent("unknown_type") == ModelGroup.REASONING
+        )
 
     def test_select_model_by_group(self, router: ModelRouter) -> None:
         """Test selecting model by group."""
@@ -99,9 +108,7 @@ class TestModelRouter:
 
     def test_select_model_by_group_string(self, router: ModelRouter) -> None:
         """Test selecting model by group string."""
-        model_name, config = asyncio.run(
-            router.select_model(model_group="code")
-        )
+        model_name, config = asyncio.run(router.select_model(model_group="code"))
 
         assert model_name == "claude-sonnet-4"
 
@@ -174,9 +181,7 @@ class TestModelRouter:
         limited_router = ModelRouter(settings=settings, circuit_registry=registry)
 
         with pytest.raises(AllProvidersFailedError) as exc_info:
-            asyncio.run(
-                limited_router.select_model(model_group=ModelGroup.REASONING)
-            )
+            asyncio.run(limited_router.select_model(model_group=ModelGroup.REASONING))
 
         assert exc_info.value.model_group == "reasoning"
         assert len(exc_info.value.attempted_models) > 0
@@ -195,18 +200,14 @@ class TestModelRouter:
 
     def test_get_available_models_for_group_string(self, router: ModelRouter) -> None:
         """Test getting available models with string group."""
-        models = asyncio.run(
-            router.get_available_models_for_group("code")
-        )
+        models = asyncio.run(router.get_available_models_for_group("code"))
 
         assert len(models) > 0
 
     def test_get_available_models_invalid_group(self, router: ModelRouter) -> None:
         """Test getting models for invalid group."""
         with pytest.raises(InvalidModelGroupError):
-            asyncio.run(
-                router.get_available_models_for_group("invalid")
-            )
+            asyncio.run(router.get_available_models_for_group("invalid"))
 
     def test_get_all_model_groups(self, router: ModelRouter) -> None:
         """Test getting all model groups info."""