fix(player): stop autoplay before unaired episodes

[Saelon600]

Closes #589.

Summary

• Resolves the next episode's TMDB air date before the autoplay prompt can open.
• Models the decision explicitly as Pending, Allowed, or Blocked so near-end resume cannot autoplay while metadata is still loading.
• Allows episodes aired before or on the current date and blocks future, missing, malformed, or unavailable metadata from automatic advancement.
• Preserves coroutine cancellation and resolves the target TMDB season/episode across season boundaries.

Why

Autoplay could advance into episodes that have not aired yet. A simple Boolean defaulting to allowed also creates a race where playback near the end can trigger before TMDB metadata returns.

Testing

• past/today/future air dates
• pending state does not open or consume the prompt
• missing episode/date, blank/malformed date, and API failure
• cancellation propagation
• season-boundary target lookup
• full Sideload unit suite, Kotlin compilation, and git diff --check

Policy

Unknown or unavailable air-date metadata blocks automatic advancement only; users can still choose episodes manually.

Scope

Android autoplay gating only. No subtitle, navigation, IPTV, backend, catalog, or app version changes.