5751e08eb1
Plex auth uses PIN-based flow, not standard OAuth2 authorization_code.
- backend/auth: POST /api/v2/pins to create PIN, GET /api/v2/pins/{id} to get authToken
- frontend/login: store pinId in sessionStorage before redirect
- frontend/callback: send pinId to backend instead of query code
- backend/index: fix dotenv path resolution for tsx (__dirname returns '.')