Mr Folio no longer has a /redeem command

[McCal-Codes]

What this changes

Removes Mr Folio's /redeem. It turned a supporter code into a Discord supporter role, handing out Coffee, Backer or Builder. Ko-fi's own Discord bot manages those roles (and Supporter), so two systems were handing out the same roles, and the bot's daily sweep could take a role from someone who still held it through Ko-fi. McCal chose to remove the command rather than give it a role of its own.

• /redeem is already unregistered from the server (done through the API on 2 Oct); this removes the code behind it.
• Gone: redeem.mjs and its tests, the command's definition and the private-answer plumbing, the daily sweep (scheduled), the D1 binding, and the settings only it used (SUPPORTER_KEYS, WITHDRAWN, ROLE_COFFEE, ROLE_BACKER, ROLE_BUILDER, the cron).
• Kept: the read-only commands and the Get release pings button. The two role calls it needs moved to discord.mjs. wrangler.toml now has just GUILD_ID and ROLE_UPDATES.
• tools/folio-bot/README.md says there is no /redeem and why; schema.sql marks discord_roles as unused. The table is kept, not dropped.
• A code is still redeemed in Folio, under Settings › Supporter, and from the email's Add to Folio button. Nothing about that changes.

How I checked it

• node --test in tools/folio-bot: 36 pass (50 before; the 14 that went are /redeem's). tools/kofi-worker: 36 pass.
• wrangler deploy --dry-run: 16 KiB, with only GUILD_ID and ROLE_UPDATES as variables, no database and no cron.
• Not deployed. The live bot still has the old code, which is harmless now: Discord no longer lists the command, so nothing can call it. Deploying (tools/folio-bot, ~/dev/folio-site/node_modules/.bin/wrangler deploy) removes the D1 binding and the cron, which is intended.

Cheap way out: revert, and re-register the command with register.mjs.

• No app change, so no CHANGELOG line (REL-7 skipped)