Add option to repeat the current video

[hymansun]

Summary

• add a synced repeatCurrentVideo setting, defaulting to off
• expose a "Repeat current video" checkbox in the Video settings section
• loop the current <video> when enabled while preserving the existing auto-next behavior when disabled
• add locale strings for English, Simplified Chinese, Traditional Chinese, and Japanese

Test

• npm run build

[jason5ng32]

Thanks for the contribution, @hymansun — but I don't think I can merge this one. Let me explain the reasoning so you can decide what to do with the branch.

Macify is built around random playback as a core behavior, not as a default that users might want to override:

1. Videos are always shuffled. Even when a user picks a specific category, playback stays random within that category — that's the intended experience, not a limitation.
2. As a consequence, every new tab, page refresh, and click on the bottom-right refresh button is supposed to land on a fresh random video.
3. A "Repeat current video" toggle sits above all of that and conflicts with both points. For example: with the option enabled, what should the refresh button do? Restart the same video from the beginning, or pick a new one? Either answer breaks one of the two expectations above.

That's just one example of the conflict — and I want to be upfront that even if that specific case were resolved, I still wouldn't want to add a "repeat current video" option, because it cuts against the product's core idea.

If this is something you personally want, I'd suggest keeping the change on your own fork. Really appreciate the effort you put in here, but I'll have to pass on merging.