- Add mail.GetQuota() using doveadm quota get
- Fix UserWithQuota response struct
- Fix frontend NaN display with Unknown fallback
- Update field names to camelCase (usedQuota)
- Prefill domain part in forms (e.g. input + @domain.com)
- Use native <dialog> element for modals
- Show error messages instead of alert()
- Cleaner input group styling