Initial commit: Arb Pulse monolith with CI and optional Fly deploy.

Real-time BTC cross-exchange arbitrage detection (Kraken, Bybit, OKX, Binance)
with React dashboard, GitHub Actions CI, and documented Fly.io deploy workflow.

Co-authored-by: Cursor <cursoragent@cursor.com>

web/src/format.ts

@@ -0,0 +1,26 @@
+export function usd(n: number, digits = 2): string {
+  return n.toLocaleString("en-US", { minimumFractionDigits: digits, maximumFractionDigits: digits });
+}
+
+export function pct(fraction: number, digits = 3): string {
+  return `${(fraction * 100).toFixed(digits)}%`;
+}
+
+export function btc(n: number, digits = 5): string {
+  return n.toFixed(digits);
+}
+
+export function ago(ts: number, now: number): string {
+  const s = Math.max(0, Math.round((now - ts) / 1000));
+  if (s < 60) return `${s}s`;
+  const m = Math.floor(s / 60);
+  return `${m}m ${s % 60}s`;
+}
+
+export function timeOf(ts: number): string {
+  return new Date(ts).toLocaleTimeString("en-US", { hour12: false });
+}
+
+export function clsx(...parts: Array<string | false | null | undefined>): string {
+  return parts.filter(Boolean).join(" ");
+}