Summary

• Add support for custom video CDN hosts, inspired by the host override behavior in https://github.com/Kanda-Akihito-Kun/ccb.
• Replace known media CDN hosts while avoiding API-like hosts, and persist the custom host in settings.
• Integrate the custom CDN entry at the bottom of the existing CDN selector so no extra settings row is added.

Details

• Supports entering either a host or a full URL, normalizing it to a host before saving.
• Custom CDN takes priority for video media URLs; choosing any built-in CDN clears the custom override.
• The player-side CDN menu and the video settings page share the same selector/result flow.
• Adds focused tests for host normalization, media CDN replacement, and API-host avoidance.