Add native Twitch VIP rewards and i18n updates

[Jamesllllllllll]

Summary

Finish the current Twitch and internationalization work across the dashboard, bot, and Twitch panel.

What Changed

• added app-owned Twitch channel point rewards for VIP token automation, including the migration, EventSub handling, settings UI, and test coverage
• documented the StreamElements -> Streamer.bot tip relay flow directly in owner settings with step-by-step instructions
• completed the panel and bot i18n work, including owner-controlled bot locale, panel locale persistence and picker polish, localized translation-help UI, and shared VIP automation copy
• hardened channel point reward setup so Affiliate/Partner eligibility and reward conflicts warn cleanly without taking the rest of the bot offline

How To Test

1. Run
   pm run format.
2. Run
   pm run lint.
3. Run
   pm run check:i18n.
4. Run
   pm run typecheck.
5. Run
   pm run test.
6. Run
   pm run build.
7. Run
   pm run check:staged.
8. Run
   pm run check:prepush.
9. In the app, verify website language switching, panel language persistence, StreamElements instructions, and the native channel point reward setup flow on an Affiliate or Partner Twitch channel.

Screenshots Or UI Notes

• Dashboard Settings now includes localized help and instruction dialogs for StreamElements tips and app-owned channel point rewards.
• The Twitch panel language picker is now a compact two-letter selector in the top-right corner and persists a panel-specific locale choice.
• Native channel point reward setup now shows a clear warning if the channel is not Affiliate or Partner, if the reward name already exists, or if the channel has reached Twitch's custom reward limit.
• Non-English bot reply coverage is still partial outside the translated common replies.

Checklist

• I tested the change locally
• I updated docs or examples if needed
• I called out any follow-up work or known limitations

[github-actions]

Preview deployment updated.

App: https://request-bot-pr-69.jameskeezer.workers.dev
Frontend worker: request-bot-pr-69
Backend worker: request-bot-backend-pr-69