feat: prepare server 1.5.0

[Priveetee]

Summary

• add private account RSS feeds and administration controls
• restrict public proxy destinations and validate redirects and resolved addresses
• add the subscription setting that hides live and upcoming streams
• remove stale live entries from subscription feeds
• report YouTube remote-login readiness only when the full path is available
• normalize YouTube channel tab URLs
• update Server dependencies and prepare version 1.5.0

Production behavior

• users can create secret RSS feeds for all subscriptions or selected channels
• administrators control RSS availability, limits, account access and active feeds
• unauthenticated proxy requests cannot target arbitrary hosts or private network addresses
• subscription feeds can omit live and upcoming content per account
• existing RSS feeds remain disabled until the instance administrator enables RSS and configures its public base URL

Deployment requirements

No manual database migration is required. RSS is disabled by default.

Tests

Server CI, Coverage and OpenAPI workflows are the release gates. No additional local validation was run for this PR.

Rollback

Restore Server revision 4bff946a.