bugfix/spider-ssr-gate
main
- Replace hardcoded CSS custom properties with SCSS variables - Add .form-error/.form-success alert banners - Add .admin-form styles: .form-row grid, .form-group labels/inputs, focus rings, is-invalid states, placeholder styling - Style .add-admin-section heading with $font-heading, divider underline - Use button-style mixin for .btn-save (was unstyled before) - Add .form-actions bar layout - Add responsive breakpoint: stack form rows on mobile (<768px) - Consistent spacing via $spacing-* tokens throughout - Consistent border-radius via $radius-* tokens throughout