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/lib/components/LightboxModal.svelte

@@ -277,12 +277,12 @@
 						bind:value={newComment}
 						placeholder="Kommentar schreiben..."
 						maxlength={COMMENT_MAX}
-						class="flex-1 rounded-lg border border-gray-300 bg-white px-3 py-2 text-sm text-gray-900 placeholder-gray-400 focus:border-blue-500 focus:outline-none dark:border-gray-700 dark:bg-gray-800 dark:text-gray-100 dark:placeholder-gray-500"
+						class="input flex-1"
 					/>
 					<button
 						type="submit"
 						disabled={loading || !newComment.trim()}
-						class="rounded-lg bg-blue-600 px-3 py-2 text-sm font-medium text-white transition hover:bg-blue-700 active:bg-blue-700 disabled:opacity-50 dark:bg-blue-500 dark:hover:bg-blue-400 dark:active:bg-blue-400"
+						class="btn btn-primary btn-sm"
 					>
 						Senden
 					</button>