room based session management and interview result API
ticket: https://bukittechnology.atlassian.net/browse/KM-462
- Add user_id and room_id to session creation; each room maps to one
active session so re-interviews replace the previous result
- Return full InterviewResultDTO (sections, Q&A pairs, insights) from
POST /sessions/{id}/finish instead of a local file path
- Add GET /rooms/{room_id}/result endpoint to retrieve the latest
finished interview result for a room
- Add CORS middleware with ALLOWED_ORIGINS env support so browser
clients can reach the API
- Update API_CONTRACT_INTERVIEW.md and README.md to reflect all changes
