feat(ui): elegant wedding white/silver/gold redesign

Reskin the whole app via design tokens in tailwind-theme.css (remapped
color ramps) plus a define-once component layer in lib/styles/components.css
(.btn, .card, .input, .chip, .badge, .sheet, …). Buttons are muted/outlined
gold rather than flat fills. Self-host Inter + Fraunces (woff2) under the
existing font-src 'self' CSP. Restyle the shared components and the account,
admin, host, join, recover and upload screens against the new tokens.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/app.css

@@ -1,4 +1,5 @@
 @import './tailwind-theme.css';
+@import './lib/styles/components.css';
 
 /* Respect the OS "reduce motion" setting. Collapses every animation/transition
  * (HeartBurst, Skeleton pulse, diashow cross-fades, sheet/FAB slides) to a