test: add tests for FastAPI server wrapper behavior

feat: implement episode finalization and adjust session support flag

refactor: unify data format and add stateful HTTP server

fix: update edge case tests imports

fix: update tasks tests for data module

fix: update rewards tests imports

fix: update retrieval tests imports

fix: update environment tests for searcharena imports

fix: update test fixtures for new imports

feat: add training utilities module

refactor: update type hints to use built-in generic types

Refactor inference and logging mechanisms; remove log_utils.py

refactor: update environment variables and reward validation range

Add comprehensive tests for Search RL Environment