feat: complete admin panel and backend admin api migration

apps/api/src/modules/customers/customers.controller.ts

@@ -1,6 +1,8 @@
 import { Controller, Get, Param } from '@nestjs/common';
 import { CustomersService } from './customers.service';
+import { Public } from '../auth/guards';
 
+@Public() // pre-existing unauthenticated endpoint; see Phase 1 notes
 @Controller('customers')
 export class CustomersController {
   constructor(private readonly customers: CustomersService) {}