Filament v5's bundled theme.css uses Tailwind v4's CSS-first import
syntax, which broke when compiled through the app's Tailwind v3
PostCSS pipeline via the custom viteTheme() registration. The custom
theme was unedited boilerplate since it was scaffolded, with no actual
branding, so drop it and let the panel use Filament's own precompiled
default styles instead of migrating the whole frontend to Tailwind v4.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
