feat: add public listing catalog boundary

packages/contracts/package.json

@@ -8,6 +8,7 @@
     "./image": "./image.js",
     "./listing": "./listing.js",
     "./product": "./product.js",
+    "./public-listing": "./public-listing.js",
     "./public-product": "./public-product.js"
   }
 }

packages/contracts/public-listing.js

@@ -0,0 +1,17 @@
+function toIsoString(value) {
+  return value instanceof Date ? value.toISOString() : value;
+}
+
+export function toPublicListingDto(listing) {
+  return {
+    id: listing.id,
+    productName: listing.productName,
+    categoryId: listing.categoryId,
+    conditionId: listing.conditionId,
+    askingPriceMinor: listing.askingPriceMinor,
+    status: listing.status,
+    notes: listing.notes ?? null,
+    createdAt: toIsoString(listing.createdAt),
+    updatedAt: toIsoString(listing.updatedAt),
+  };
+}