Add initial seeding script for roles and promo codes

This commit introduces a new seed script located at prisma/seed.ts. The script seeds the database with default roles ('user' and 'admin') and a sample promo code ('PROMO1000' with a value of 1000). This setup helps initialize essential data for application functionality.

prisma/seed.ts

@@ -0,0 +1,34 @@
+import { PrismaClient } from '@prisma/client';
+
+const prisma = new PrismaClient();
+
+async function main() {
+  await prisma.role.create({
+    data: {
+      name: 'user',
+    },
+  });
+  await prisma.role.create({
+    data: {
+      name: 'admin',
+    },
+  });
+
+  await prisma.promoCode.create({
+    data: {
+      name: 'PROMO1000',
+      value: 1000,
+    },
+  });
+}
+
+main()
+  .then(async () => {
+    await prisma.$disconnect();
+  })
+  .catch(async (e) => {
+    console.error(e);
+    await prisma.$disconnect();
+    process.exit(1);
+  });
+