feat(agent): add redis short-term user context cache and align tests

backend/tests/integration/test_users_routes.py

@@ -44,11 +44,6 @@ class FakeUserService:
             bio=update.bio if update.bio is not None else self._user.bio,
         )
 
-    async def get_by_username(self, username: str) -> UserResponse:
-        if username != self._user.username:
-            raise HTTPException(status_code=404, detail="User not found")
-        return self._user
-
     async def search_users(self, request: UserSearchRequest) -> list[UserResponse]:
         if request.query:
             return self._search_results if self._search_results else [self._user]
@@ -191,22 +186,3 @@ def test_search_users_empty_query_returns_422() -> None:
         assert response.status_code == 422
     finally:
         app.dependency_overrides = {}
-
-
-def test_get_user_by_username_returns_404() -> None:
-    user = UserResponse(
-        id="00000000-0000-0000-0000-000000000001",
-        username="demo",
-        avatar_url=None,
-        bio=None,
-    )
-    app.dependency_overrides[get_user_service] = _override_user_service(
-        FakeUserService(user)
-    )
-
-    client = TestClient(app)
-    try:
-        response = client.get("/api/v1/users/demo")
-        assert response.status_code == 404
-    finally:
-        app.dependency_overrides = {}