Create a backend service for filtering out Uncategorized videos

[mblomdahl]

As an alternative approach to waiting for acceptance and roll-out of changes in #14 (and then wait for all the video site maintainers to actually upgrade their servers with newer PeerTube software), we can deploy a backend service that queries a PeerTube server for all videos, caches them, and returns the subset that matches our criteria.

Functional requirements:

1. Send a GET <owntube-backend>/api/peertube/<instance_hostname>/api/v1/videos/isLocal=true&categoryOneOf[]=null,2
2. Expect a response that include all local videos with category Unknown (null) or Films (2)

Non-functional requirements:

• Implemented in Node 22 with NestJS and Typescript
• No robust database persistence in initial version, use a container-local SQLite database
• Video discovery results for a host should be cached and reused between requests, i.e.
  1. in request handler; request received → emit a backend-local "check cache for instance_hostname Videos" event → return the cached results
  2. in backend-local subscriber for the "check cache for instance_hostname Videos" event; a) check when was the site last queried for channels and if it was more than 1 week ago or b) send a request and check the first page of results ordered by updatedAt (descending); then if any of a) or b) are true emit a backend-local "update cache for instance_hostname Videos" event
  3. in backend-local subscriber for the "update cache for instance_hostname Videos" event, run the Videos discovery on the target site and update the cache with new results and new cache update timestamp
• If no Videos discovery result is available in the backend-local storage, it should run the Videos discovery on the target site synchronously, cache it, and then return the results to the client
• Rate limits on the PeerTube API must be respected (dynamically, subject to rate limiting response headers)
• GitHub Actions CI/CD pipeline for deploying it to OwnTube.tv Kubernetes