transform core api codes into this project, update modules as admin/pos context modules

src/modules/pos/customers/customers.service.ts

@@ -0,0 +1,19 @@
+import { Injectable } from '@nestjs/common'
+
+@Injectable()
+export class CustomersService {
+  findAll() {
+    // TODO: Implement fetching all customers
+    return []
+  }
+
+  findOne(id: number) {
+    // TODO: Implement fetching a single customer
+    return {}
+  }
+
+  create(data: any) {
+    // TODO: Implement customer creation
+    return data
+  }
+}