refactor(ui): strip all dark: Tailwind classes (single-theme product)

Mechanical sweep of 41 files via `perl -i -pe 's{\s+dark:[\w:/\[\]\.\-]+}{}g'`.
All dark: variants were paired with light-mode counterparts already; no
elements relied on a dark:-only style.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/(applicant)/applicant/page.tsx

@@ -219,12 +219,12 @@ export default function ApplicantDashboardPage() {
               key={round.id}
               className={`flex flex-col sm:flex-row items-start sm:items-center gap-3 rounded-lg border px-4 py-3 ${
                 isUrgent
-                  ? 'border-amber-500/50 bg-amber-50 dark:bg-amber-950/20'
+                  ? 'border-amber-500/50 bg-amber-50'
                   : 'border-primary/20 bg-primary/5'
               }`}
             >
               <div className="flex items-center gap-2 min-w-0">
-                <Clock className={`h-4 w-4 shrink-0 ${isUrgent ? 'text-amber-600 dark:text-amber-400' : 'text-primary'}`} />
+                <Clock className={`h-4 w-4 shrink-0 ${isUrgent ? 'text-amber-600' : 'text-primary'}`} />
                 <span className="font-medium text-sm truncate">{round.name}</span>
                 <Badge variant={isUrgent ? 'warning' : 'default'} className="shrink-0">
                   {remaining > 0 ? formatCountdown(remaining) + ' left' : 'Closed'}