Removes RESEND_AUDIENCE_WAITLIST env var. capture_waitlist_email() now
derives audience name from request.blueprints[0] (e.g. waitlist-auth,
waitlist-suppliers), lazily creates it via Resend API on first signup,
and caches the ID in a new resend_audiences table. Zero config beyond
RESEND_API_KEY — adding @waitlist_gate to any new blueprint auto-creates
its audience on first use.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
77d801e326