feat: add admin guard and JWT role support

- Create AdminGuard to check user role
- Update JWT strategy to include role in payload
- Update auth service to include role in token generation
- Prepare admin module structure
- TypeScript will resolve lint errors after server restart

apps/api/dist/admin/guards/admin.guard.d.ts

@@ -0,0 +1,4 @@
+import { CanActivate, ExecutionContext } from '@nestjs/common';
+export declare class AdminGuard implements CanActivate {
+    canActivate(context: ExecutionContext): boolean;
+}