Fix public playlist request and mobile layout

[Jamesllllllllll]

Summary

Fix a few public playlist UI regressions on the channel slug page.

What Changed

• fixed the collapsed played-history card so it no longer causes slight horizontal page overflow
• tightened the public playlist manager mobile layout so the action buttons stay centered and the empty state has padding
• replaced the oversized special-request button grid with a denser artist-based request flow for random and streamer choice requests

How To Test

1. Open a public / playlist page on desktop and mobile widths.
2. Confirm the page no longer scrolls horizontally when the played history section is collapsed.
3. Confirm Shuffle, Clear playlist, and Reset session stay inside the playlist area on smaller screens.
4. Confirm the special request block accepts an artist name, lets you choose random or streamer choice plus regular or VIP, and submits correctly.

Screenshots Or UI Notes

Public playlist only. No panel changes.

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-61.jameskeezer.workers.dev
Frontend worker: request-bot-pr-61
Backend worker: request-bot-backend-pr-61