feat: configure and display public seller descriptions

apps/api/tests/http/public-listing-routes.test.js

@@ -37,6 +37,7 @@ function createTestApp() {
           askingPriceMinor: 2499,
           status: 'PENDING',
           sellerDisplayName: 'Pika Collectibles',
+          sellerDescription: 'Independent Pokémon collector.',
           sellerContactEmail: 'hello@pika.example',
           sellerContactPhone: null,
         };
@@ -76,6 +77,7 @@ test('returns a public listing detail or a not-found response', async (testConte
   assert.equal(detailResponse.statusCode, 200);
   assert.equal('inventoryItemId' in detailResponse.json().data, false);
   assert.equal(detailResponse.json().data.sellerDisplayName, 'Pika Collectibles');
+  assert.equal(detailResponse.json().data.sellerDescription, 'Independent Pokémon collector.');
   assert.equal(detailResponse.json().data.sellerContactEmail, 'hello@pika.example');
   assert.equal(missingResponse.statusCode, 404);
   assert.equal(missingResponse.json().error.code, 'LISTING_NOT_FOUND');

apps/api/tests/http/public-product-routes.test.js

@@ -22,6 +22,7 @@ function createTestApp() {
           slug,
           description: 'A friendly plush.',
           sellerDisplayName: 'Pika Collectibles',
+          sellerDescription: 'Independent Pokémon collector.',
           sellerContactEmail: 'hello@pika.example',
           sellerContactPhone: null,
           createdAt: new Date('2026-09-07T00:00:00.000Z'),
@@ -55,6 +56,7 @@ test('returns a public product without private seller identity', async (testCont
     releaseYear: null,
     tags: [],
     sellerDisplayName: 'Pika Collectibles',
+    sellerDescription: 'Independent Pokémon collector.',
     sellerContactEmail: 'hello@pika.example',
     sellerContactPhone: null,
     createdAt: '2026-09-07T00:00:00.000Z',