feat(market): add CoinGecko market data panel with cached /api/market endpoint

lib/format.ts

@@ -45,3 +45,47 @@ export function formatTimestamp(value: string): string {
     timeStyle: "short"
   }).format(date);
 }
+
+export function formatUsdPrice(value: number): string {
+  if (!Number.isFinite(value)) {
+    return "-";
+  }
+
+  if (Math.abs(value) >= 1) {
+    return value.toLocaleString("en-US", {
+      style: "currency",
+      currency: "USD",
+      minimumFractionDigits: 2,
+      maximumFractionDigits: 2,
+    });
+  }
+
+  return value.toLocaleString("en-US", {
+    style: "currency",
+    currency: "USD",
+    minimumFractionDigits: 2,
+    maximumFractionDigits: 8,
+  });
+}
+
+export function formatUsdCompact(value: number | null): string {
+  if (value === null || !Number.isFinite(value)) {
+    return "-";
+  }
+
+  return value.toLocaleString("en-US", {
+    style: "currency",
+    currency: "USD",
+    notation: "compact",
+    maximumFractionDigits: 2,
+  });
+}
+
+export function formatSignedPercent(value: number | null): string {
+  if (value === null || !Number.isFinite(value)) {
+    return "-";
+  }
+
+  const sign = value > 0 ? "+" : "";
+  return `${sign}${value.toFixed(2)}%`;
+}