refactor: centralize number formatting with locale-aware utility

web/src/lib/utils.ts

@@ -8,3 +8,26 @@ export function cn(...inputs: ClassValue[]) {
 /** Shared tooltip content styling for bits-ui Tooltip.Content */
 export const tooltipContentClass =
   "z-50 bg-card text-card-foreground text-xs border border-border rounded-md px-2.5 py-1.5 shadow-md max-w-72";
+
+export interface FormatNumberOptions {
+  /** Include sign for positive numbers (default: false) */
+  sign?: boolean;
+  /** Maximum fraction digits (default: 0 for integers) */
+  maximumFractionDigits?: number;
+}
+
+/**
+ * Format a number with locale-aware thousands separators.
+ * Uses browser locale via Intl.NumberFormat.
+ */
+export function formatNumber(num: number, options: FormatNumberOptions = {}): string {
+  const { sign = false, maximumFractionDigits = 0 } = options;
+  const formatted = new Intl.NumberFormat(undefined, {
+    maximumFractionDigits,
+  }).format(num);
+
+  if (sign && num >= 0) {
+    return `+${formatted}`;
+  }
+  return formatted;
+}