feat(episodes): add episode availability tracking and sync

[0xSysR3ll]

Description

This allows Jellyseerr to track the availability status of individual episodes, enabling better status reporting for partially available seasons.

Screenshot (if UI-related)

To-Dos

• [x] Successful build pnpm build
• [x] Translation keys pnpm i18n:extract
• [x] Database migration (if required)

Issues Fixed or Closed

• Fixes #270