v3.10.1-fix-catchup

Custom build for IPTV catchup compatibility improvements.

Changes:

• improve catchup playback behavior in the built-in web player
• show clearer upstream catchup error messages
• add configurable recent catchup blocking window presets
• align recent catchup blocking with upstream declared timeshift length
• expose x-r2h-timeshift-length in generated M3U output
• include RTSP catchup stability fixes and upstream failure mitigation

Full Changelog: v3.10.1-fix-catchup...v3.10.1-fix-catchup