Rewrite dashboard frontend in Tailwind CSS

Drop the bespoke stylesheet and rebuild the seven dashboard pages with
Tailwind utility classes, served via the play CDN with a small set of
custom @apply'd component classes (.nav-link, .kpi-card, .panel, .tag,
.table-data, .btn-primary, .btn-ghost) defined inline in the base template.
This gives the dashboards a modern, consistent visual language without
introducing a Node build step into the image.

Layout, palette, typography and component shapes all updated: indigo and
violet brand gradient on the brand mark, slate text scale, emerald and
rose for positive and negative figures, violet for investments and amber
for tax. Charts pick up Inter and the slate/indigo tones via the existing
Chart.js defaults.

Author: xhico