Agregar campo username a User entity y DTO

- Columna username (unique, nullable) en auth.users
- Campo username en CreateUserDto y UpdateUserDto

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

src/modules/kimi/kimi.module.ts

@@ -0,0 +1,12 @@
+import { Module, Global } from "@nestjs/common";
+import { ConfigModule } from "@nestjs/config";
+import { KimiService } from "./kimi.service";
+import kimiConfig from "../../config/integrations/kimi.config";
+
+@Global()
+@Module({
+  imports: [ConfigModule.forFeature(kimiConfig)],
+  providers: [KimiService],
+  exports: [KimiService],
+})
+export class KimiModule {}