Adds token expiry checking and automatic refresh to prevent intermittent
401 errors when the cached session token expires between interactions.
- Check token expiry (60s buffer) before each API call
- Add 401 interceptor that retries once with refreshed token
- Explicitly enable autoRefreshToken in Supabase client
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>