Add SMS consent logging for Twilio compliance

Log phone, IP, and user agent to sms_consents table before sending
verification SMS. Add disclosure text to login form.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

db/queries.sql

@@ -132,3 +132,6 @@ SELECT * FROM rsvps WHERE id = ?;
 
 -- name: UpdateRsvp :exec
 UPDATE rsvps SET name = ?, note = ?, plus_one = ? WHERE id = ?;
+
+-- name: CreateSmsConsent :exec
+INSERT INTO sms_consents (phone, ip_address, user_agent) VALUES (?, ?, ?);