chore(repo): restructure as monorepo with server and client workspaces

- move NestJS app into server/ subdirectory
- add client/ React+TypeScript (Vite) app with Hello World
- update docker-compose to build and run both services
- add root package.json declaring npm workspaces
- update .gitignore to cover node_modules and dist at all depths

server/src/scenario/dto/scenario-export.dto.ts

@@ -0,0 +1,54 @@
+import { ApiProperty, ApiPropertyOptional } from "@nestjs/swagger";
+import { Type } from "class-transformer";
+import {
+  IsArray,
+  IsIn,
+  IsInt,
+  IsNotEmpty,
+  IsOptional,
+  IsString,
+  Min,
+  ValidateNested,
+} from "class-validator";
+import { StepType } from "../scenario-step.entity";
+
+export class ScenarioStepExportDto {
+  @ApiProperty()
+  @IsInt()
+  @Min(0)
+  order: number;
+
+  @ApiProperty({ enum: ["login", "exec", "sign"] })
+  @IsIn(["login", "exec", "sign"])
+  type: StepType;
+
+  @ApiProperty()
+  @IsString()
+  @IsNotEmpty()
+  sessionName: string;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsString()
+  @IsNotEmpty()
+  execCode: string | null;
+
+  @ApiPropertyOptional()
+  @IsOptional()
+  @IsString()
+  @IsNotEmpty()
+  validateCode: string | null;
+}
+
+export class ScenarioExportDto {
+  @ApiProperty()
+  @IsString()
+  @IsNotEmpty()
+  name: string;
+
+  @ApiProperty({ type: [ScenarioStepExportDto] })
+  @IsArray()
+  @ValidateNested({ each: true })
+  @Type(() => ScenarioStepExportDto)
+  steps: ScenarioStepExportDto[];
+}