feat: prepare server 1.4.0

[Priveetee]

Summary

• add grouped YouTube search filter APIs
• enforce blocked content on stream and recommendation routes
• serve and cache YouTube subtitle content through Server
• add configurable account session lifetime
• preload adaptive SABR initialization ranges
• filter unavailable YouTube Takeout videos
• align PipePipeExtractor and the Server version with TypeType 1.4.0

Production behavior

• YouTube subtitle tracks remain available through a same-origin endpoint
• subtitle throttling returns typed errors
• blocked channels and videos cannot bypass filters through alternate identities
• SABR startup remains stable when initialization media is delayed
• account sessions default to 30 days and accept a configured lifetime from 1 to 365 days

Deployment requirements

AUTH_SESSION_TTL_DAYS is optional and defaults to 30. No database migration is required.

When a YouTube proxy is configured, it must remain reachable because Server no longer silently bypasses it.

Tests

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

Rollback

Restore Server revision a8eeae78.