feat: 重构关卡接口

src/modules/level/dto/complete-level.dto.ts

@@ -1,5 +1,6 @@
 import { ApiProperty } from '@nestjs/swagger';
-import { IsNotEmpty, IsNumber, IsString, Min } from 'class-validator';
+import { IsNotEmpty, IsNumber, Min } from 'class-validator';
+import { NextLevelDto } from './next-level.dto';
 
 export class CompleteLevelRequestDto {
   @ApiProperty({ description: '通关时长（秒）' })
@@ -18,4 +19,11 @@ export class CompleteLevelResponseDto {
 
   @ApiProperty({ description: '通关时长（秒）' })
   timeSpent!: number;
+
+  @ApiProperty({
+    description: '下一个待通关的关卡（全部通关时为 null）',
+    nullable: true,
+    type: NextLevelDto,
+  })
+  nextLevel!: NextLevelDto | null;
 }