feat: ability to use jellyfin access token for user authentication

[herrrta]

Description

• updates jellyfin auth endpoints to:
  • persist jellyfin access token along user login
  • optionally allow login with existing jellyifn access token to prevent exceeding any admin defined user session limits
• updates auth middleware to also acccept api keys for jellyfin user auth
• adds #2243

How Has This Been Tested?

Ran dev locally and tested endpoints using postman. I made sure i can login and use the provided jellyfinAuthToken in the login response.

I used this auth token to update my X-API-Key header to then access /api/v1/auth/me while also ensuring cookies were empty to make sure this authenticated using only the key. It properly authenticated to the right user each time.

Screenshots / Logs (if applicable)

Checklist:

• [X] I have read and followed the contribution guidelines.
• [X] Disclosed any use of AI (see our policy)
• [X] I have updated the documentation accordingly.
• [X] All new and existing tests passed.
• [X] Successful build pnpm build
• [X] Translation keys pnpm i18n:extract
• [X] Database migration (if required)