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/test/app.harness.ts

@@ -0,0 +1,89 @@
+import { INestApplication, ValidationPipe } from "@nestjs/common";
+import { Test, TestingModule } from "@nestjs/testing";
+import { TypeOrmModule } from "@nestjs/typeorm";
+import { ConfigModule } from "@nestjs/config";
+import { ScheduleModule } from "@nestjs/schedule";
+jest.mock("@nestjs/common", () => {
+  const actual = jest.requireActual("@nestjs/common");
+  // eslint-disable-next-line @typescript-eslint/no-require-imports
+  const log = require("debug")("test");
+  // eslint-disable-next-line @typescript-eslint/no-require-imports
+  const { Logger } = require("@nestjs/common/services/logger.service");
+
+  Logger.prototype.error = function (
+    message: unknown,
+    stack?: string,
+    context?: string,
+  ) {
+    const ctx = context ?? this.context ?? "App";
+    log(`[${ctx}]`, "error", message, ...(stack ? [stack] : []));
+  };
+
+  for (const level of ["log", "warn", "debug", "verbose", "fatal"] as const) {
+    Logger.prototype[level] = function (message: unknown, context?: string) {
+      const ctx = context ?? this.context ?? "App";
+      log(`[${ctx}]`, level, message);
+    };
+  }
+
+  return actual;
+});
+
+import { AuthModule } from "../src/auth/auth.module";
+import { BrowserModule } from "../src/browser/browser.module";
+import { SessionModule } from "../src/session/session.module";
+import { EnvironmentModule } from "../src/environment/environment.module";
+import { ScenarioModule } from "../src/scenario/scenario.module";
+import { McpModule } from "../src/mcp/mcp.module";
+import { SessionEntity } from "../src/session/session.entity";
+import { EnvironmentEntity } from "../src/environment/environment.entity";
+import { ScenarioEntity } from "../src/scenario/scenario.entity";
+import { ScenarioStepEntity } from "../src/scenario/scenario-step.entity";
+import { ScenarioRunEntity } from "../src/scenario/scenario-run.entity";
+import { ScenarioRunStepEntity } from "../src/scenario/scenario-run-step.entity";
+import { ScenarioRunLogEntity } from "../src/scenario/scenario-run-log.entity";
+import { HealthController } from "../src/health/health.controller";
+import { HttpExceptionFilter } from "../src/filters/http-exception.filter";
+import { LoggingInterceptor } from "../src/interceptors/logging.interceptor";
+import { validateAppConfig } from "../src/config/app.config";
+
+export async function buildTestApp(): Promise<INestApplication> {
+  const module: TestingModule = await Test.createTestingModule({
+    imports: [
+      ConfigModule.forRoot({
+        isGlobal: true,
+        ignoreEnvFile: true,
+        validate: validateAppConfig,
+      }),
+      TypeOrmModule.forRoot({
+        type: "better-sqlite3",
+        database: ":memory:",
+        entities: [
+          SessionEntity,
+          EnvironmentEntity,
+          ScenarioEntity,
+          ScenarioStepEntity,
+          ScenarioRunEntity,
+          ScenarioRunStepEntity,
+          ScenarioRunLogEntity,
+        ],
+        synchronize: true,
+      }),
+      ScheduleModule.forRoot(),
+      AuthModule,
+      BrowserModule,
+      SessionModule,
+      EnvironmentModule,
+      ScenarioModule,
+      McpModule,
+    ],
+    controllers: [HealthController],
+  }).compile();
+
+  const app = module.createNestApplication();
+  app.useGlobalPipes(new ValidationPipe({ transform: true, whitelist: true }));
+  app.useGlobalFilters(new HttpExceptionFilter());
+  app.useGlobalInterceptors(new LoggingInterceptor());
+  await app.init();
+  return app;
+}