Add HTTP endpoint to retrieve saved session images by session ID.
Images are saved during car_fueling progression stage.
- Add GET /session-image/{session_id} endpoint
- Search images directory for files matching session ID pattern
- Return most recent image if multiple exist
- Proper error handling (404 for not found, 500 for errors)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>