Landing chat

The public login-page assistant creates and updates support sessions through POST /api/v1/landing/chat.

Database ownership

• supabase_admin owns public.landing_sessions and applies schema changes.
• postgres is the API role and receives only SELECT, INSERT, and UPDATE.
• Migration 026_landing_sessions_api_privileges.sql repairs existing databases.
• Request handling does not create indexes or perform other owner-only DDL.