List all API keys for the authenticated user (via Edge Function)
Returns all API keys (active and revoked) created by the user, along with counts showing usage against the limit.
Security:
Headers (from edge function): X-Edge-Secret: Shared secret X-User-Id: Supabase user ID (already validated) X-User-Email: User email (already validated)
Returns: ListAPIKeysResponse with keys list and counts (total, active, max)