feat(web): add Next.js portfolio with live MT5 dashboard

- Linear design system (dark canvas, lavender accent)
- Live account stats, open positions, pending orders (30s polling)
- Trade history with equity curve chart
- Backtest results table
- Proxy API routes — MT5_BASE_URL server-side only, never exposed to browser
- Deploy on Vercel: set MT5_BASE_URL env var

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

web/lib/format.ts

@@ -0,0 +1,22 @@
+export function formatCurrency(n: number, currency = "USD"): string {
+  return new Intl.NumberFormat("en-US", {
+    style: "currency", currency,
+    minimumFractionDigits: 2,
+    maximumFractionDigits: 2,
+  }).format(n);
+}
+
+export function formatPct(n: number, decimals = 1): string {
+  return `${n >= 0 ? "+" : ""}${n.toFixed(decimals)}%`;
+}
+
+export function formatDate(iso: string): string {
+  return new Date(iso).toLocaleString("en-US", {
+    month: "short", day: "numeric",
+    hour: "2-digit", minute: "2-digit",
+  });
+}
+
+export function formatPrice(n: number, digits = 2): string {
+  return n.toFixed(digits);
+}