POST /api/dev/set-plan { plan: 'free'|'pro'|'legend' } — requireUser, sets the
caller's own profile.plan via Prisma. Refuses on production URL (same guard as
the cooldown testMode: appUrl includes rebreak.org && !includes staging). Lets
the __DEV__ tier-toggle work without admin rights. Does NOT weaken updateProfile.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>