Extract shared purchase page pricing utilities.

Move interval formatting, price labels, and free-price detection into reusable helpers for the checkout redesign.

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

apps/dashboard/src/components/payments/purchase-utils.ts

@@ -0,0 +1,43 @@
+export function shortenedInterval(interval: [number, string]): string {
+  if (interval[0] === 1) {
+    return interval[1];
+  }
+  return `${interval[0]} ${interval[1]}s`;
+}
+
+export function getPriceLabel(interval: [number, string] | undefined): string {
+  if (!interval) {
+    return "One-time";
+  }
+  const [count, unit] = interval;
+
+  if (count === 1) {
+    if (unit === "day") {
+      return "Daily";
+    } else if (unit === "week") {
+      return "Weekly";
+    } else if (unit === "month") {
+      return "Monthly";
+    } else if (unit === "year") {
+      return "Yearly";
+    } else {
+      return `Every ${unit}`;
+    }
+  }
+
+  if (unit === "day") {
+    return `Every ${count} days`;
+  } else if (unit === "week") {
+    return `Once every ${count} weeks`;
+  } else if (unit === "month") {
+    return `Every ${count} months`;
+  } else if (unit === "year") {
+    return `Every ${count} years`;
+  } else {
+    return `Every ${count} ${unit}s`;
+  }
+}
+
+export function isFreePrice(usd: string | undefined): boolean {
+  return usd === "0" || usd === "0.00";
+}