fix(tags): unblock production D1 migration for suggestions

[KiranRajeev-KV]

Summary

• Wrap the three quota/kill-switch CASE … END expressions in migration 0006_luxuriant_boomer.sql with parentheses.
• This addresses the remote D1 incomplete input: SQLITE_ERROR [7500] seen in the production deployment. Cloudflare's D1 SQL splitter has a documented issue with unparenthesized SELECT CASE … END inside triggers; the trigger logic and limits are unchanged.

Verification

• Applied migrations 0000 through 0006 to a fresh temporary local D1 database with Wrangler 4.123.0.
• Confirmed the trigger still rejects attempts when disabled, at the per-user daily limit, and at the global monthly limit.
• pnpm run build, pnpm run format:check, and git diff --check passed.

Release note

The prior production run stopped at migration 0006, before Worker deployment. After merging this PR into prod, the deployment workflow should retry the pending migration automatically before deploying. Remote D1 parsing cannot be verified from local tests alone; check that the migration and deploy steps both complete successfully. Keep the tag-suggestion switch disabled until the deployed endpoint and quota accounting are smoke-tested.