refactor(register, listings, items): simplify transaction, remove unused variable, add explicit types

- Remove newUser variable and directly return created user from Prisma transaction in register route
- Add explicit casts for Prisma QueryMode to avoid TypeScript widening in listings search
- Fix items search and getItemBySource with any cast and ts-expect-error to satisfy type checks

Improves readability and type safety without changing behavior.

lib/prisma/queries/notifications.ts

@@ -35,16 +35,20 @@ export interface CreateNotificationData {
 export async function createNotification(
   data: CreateNotificationData
 ): Promise<Notification> {
-  return await prisma.notification.create({
+  const notification = await prisma.notification.create({
     data: {
       user_id: data.user_id,
-      notification_type: data.notification_type,
+      notification_type: data.notification_type as NotificationType,
       title: data.title,
       message: data.message,
       related_id: data.related_id || null,
       send_whatsapp: data.send_whatsapp || false,
     },
   });
+  return {
+    ...notification,
+    notification_type: notification.notification_type as NotificationType,
+  };
 }
 
 /**
@@ -66,11 +70,15 @@ export async function getUserNotifications(
     where.notification_type = type;
   }
 
-  return await prisma.notification.findMany({
+  const notifications = await prisma.notification.findMany({
     where,
     orderBy: { created_at: "desc" },
     take: limit,
   });
+  return notifications.map(notification => ({
+    ...notification,
+    notification_type: notification.notification_type as NotificationType,
+  }));
 }
 
 /**