Run Call Unit Tests Endpoint

Run call unit tests for a specific agent.

This endpoint:

1. Fetches the agent's current configuration
2. Retrieves test cases from db-svc (conversation contexts marked as unit tests)
3. Runs each test case against the agent's current settings
4. Calculates similarity scores using LLM-as-judge
5. Saves results to db-svc
6. Returns the test results

Args: request: RunCallUnitTestsRequest with agent_id, optional test_ids, and similarity_threshold

Returns: RunCallUnitTestsResponse with all test run results