feat: Complete NestJS backend scaffold — 22 modules, 39 entities, WebSocket gateway

Full backend rewrite from Rust/Axum to NestJS/TypeScript.
- 22 feature modules (auth, servers, wipes, maps, plugins, players, console,
  chat, team, notifications, settings, schedules, analytics, alerts, status,
  store, webstore, admin, setup, migration, users, licenses)
- 39 TypeORM entities matching PostgreSQL schema (12 migrations)
- Common infrastructure: JWT/RBAC guards, decorators, exception filter
- NATS service with pub/sub/request-reply
- Socket.IO WebSocket gateway with NATS bridge
- Docker: NestJS Dockerfile + updated docker-compose.yml
- Zero compile errors (npx tsc --noEmit clean)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-nest/src/modules/settings/dto/update-domain.dto.ts

@@ -0,0 +1,25 @@
+import { IsString, IsOptional, Matches } from 'class-validator';
+import { ApiProperty } from '@nestjs/swagger';
+
+export class UpdateDomainDto {
+  @ApiProperty({
+    description: 'Subdomain (alphanumeric and hyphens only)',
+    example: 'myserver',
+    required: false,
+  })
+  @IsString()
+  @IsOptional()
+  @Matches(/^[a-z0-9-]+$/, {
+    message: 'Subdomain can only contain lowercase letters, numbers, and hyphens',
+  })
+  subdomain?: string;
+
+  @ApiProperty({
+    description: 'Custom domain',
+    example: 'play.myserver.com',
+    required: false,
+  })
+  @IsString()
+  @IsOptional()
+  custom_domain?: string;
+}