FEAT: add authProvider field to user response

- Add authProvider to user entity DTO
- Update user service to include authProvider
- Update auth controller response

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/modules/auth/auth.controller.ts

@@ -215,7 +215,8 @@ export class AuthController {
 
     const { username } = body;
 
-    return this.authClient.resetPassword({ username }, metadata);
+    await this.authClient.resetPassword({ username }, metadata);
+    return { authProvider: process.env.AUTH_PROVIDER || 'cognito' };
   }
 
   @ApiInternalOnlyEndpoint()