Initial marketplace implementation

Full-stack marketplace for buying/selling second-hand items.
React 19 + TypeScript + Tailwind CSS v4 frontend with 17 screens,
Express + Prisma + Socket.io backend, Stripe payments, JWT auth.

Deployed at https://marketplace.173.212.212.157.sslip.io/

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/src/utils/format.ts

@@ -0,0 +1,31 @@
+export function formatCurrency(amount: number): string {
+  return new Intl.NumberFormat('en-US', {
+    style: 'currency',
+    currency: 'USD',
+    minimumFractionDigits: 0,
+    maximumFractionDigits: 2,
+  }).format(amount);
+}
+
+export function formatDate(date: string): string {
+  const d = new Date(date);
+  const now = new Date();
+  const diff = now.getTime() - d.getTime();
+  const minutes = Math.floor(diff / 60000);
+  const hours = Math.floor(diff / 3600000);
+  const days = Math.floor(diff / 86400000);
+
+  if (minutes < 1) return 'Just now';
+  if (minutes < 60) return `${minutes}m ago`;
+  if (hours < 24) return `${hours}h ago`;
+  if (days < 7) return `${days}d ago`;
+  return d.toLocaleDateString('en-US', { month: 'short', day: 'numeric' });
+}
+
+export function formatDateFull(date: string): string {
+  return new Date(date).toLocaleDateString('en-US', {
+    year: 'numeric',
+    month: 'long',
+    day: 'numeric',
+  });
+}