Add richer request modes across chat and panel

[Jamesllllllllll]

Summary

Adds richer request modes and command handling across chat, the public playlist page, and the Twitch panel. Related to #2.

What Changed

• add shared parsing for *random, *choice, and *any request modifiers
• support !position, bare !vip, and decimal !addvip <user> <amount> in chat
• let viewers submit and edit random or streamer-choice requests from the website and Twitch panel
• update !how so it reflects the current commands and links to the streamer playlist page
• disable panel VIP request actions when the viewer does not have enough VIP tokens
• keep *official out of scope for this PR

How To Test

1. Run npm run check:staged.
2. Run npm run check:prepush.
3. Run $env:VITE_TWITCH_EXTENSION_API_BASE_URL='https://rocklist.live'; npm run build:extension:panel.
4. In chat, verify !how, !position, !vip, !addvip <user> 0.5, !sr artist *random, and !sr artist *choice.
5. On a public playlist page and in the Twitch panel, verify Random song and Streamer choice request actions and the disabled VIP state when tokens are unavailable.

Screenshots Or UI Notes

Public playlist search and the Twitch panel now expose Random song and Streamer choice quick actions. Streamer-choice requests stay as placeholders instead of binding to a specific catalog song.

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-57.jameskeezer.workers.dev
Frontend worker: request-bot-pr-57
Backend worker: request-bot-backend-pr-57