Add chatter blacklist controls and fix search totals

[Jamesllllllllll]

Summary

Add chatter-based command blacklisting in moderation and fix song search totals so the summary reflects the full filtered result set across pages.

What Changed

• Added a chatter blacklist manager to the moderation dashboard using the existing Twitch user lookup flow, including current-chatter prioritization and unblock actions.
• Updated EventSub chat command handling so blocked chatters are ignored for all bot commands, including request commands and informational commands like !how.
• Made the shared song search panel support total-based summaries and updated both the public channel page and the generic /search page to show correct totals across pagination.
• Added backend search filtering so public playlist search totals stay correct when blacklisted songs are hidden.
• Added chat-command tests covering blocked chatter behavior.

How To Test

1. Run npm run typecheck.
2. Run npm run format.
3. Run npm run lint.
4. Run npm run test.
5. Run npm run build.
6. In /dashboard/moderation, search for a Twitch user in the new chatter blacklist section, block them, then confirm the bot ignores their commands in chat.
7. Unblock the same user and confirm commands work again.
8. On /$slug, toggle hidden blacklisted songs and verify the Found X songs summary stays consistent across pages.
9. On /search, confirm the Found X songs summary reflects the total results, not just the current page size.

Screenshots Or UI Notes

• Moderation now includes a Chatter blacklist card with Twitch user search, current-chatter prioritization, and unblock actions.
• Search summaries on both the public playlist page and /search now display total filtered matches across pages.

Checklist

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

Closes #6

[github-actions]

Preview deployment updated.

App: https://request-bot-pr-36.jameskeezer.workers.dev
Frontend worker: request-bot-pr-36
Backend worker: request-bot-backend-pr-36