feat: add nestjs api and worker skeletons

backend/apps/worker/src/main.ts

@@ -0,0 +1,20 @@
+import { INestApplicationContext, Type } from '@nestjs/common';
+import { NestFactory } from '@nestjs/core';
+import { WorkerModule } from './worker.module';
+
+type ContextFactory = (
+  module: Type<unknown>,
+) => Promise<INestApplicationContext>;
+
+export async function bootstrapWorker(
+  createContext: ContextFactory = (module) =>
+    NestFactory.createApplicationContext(module),
+): Promise<INestApplicationContext> {
+  const app = await createContext(WorkerModule);
+  app.enableShutdownHooks();
+  return app;
+}
+
+if (require.main === module) {
+  void bootstrapWorker();
+}

backend/apps/worker/src/worker.bootstrap.spec.ts

@@ -0,0 +1,16 @@
+import { bootstrapWorker } from './main';
+
+describe('bootstrapWorker', () => {
+  it('creates an application context without starting an HTTP listener', async () => {
+    const close = jest.fn().mockResolvedValue(undefined);
+    const enableShutdownHooks = jest.fn();
+    const appContext = { close, enableShutdownHooks };
+    const createContext = jest.fn().mockResolvedValue(appContext);
+
+    const app = await bootstrapWorker(createContext as never);
+
+    expect(createContext).toHaveBeenCalledTimes(1);
+    expect(enableShutdownHooks).toHaveBeenCalledTimes(1);
+    expect(app).toBe(appContext);
+  });
+});

backend/apps/worker/src/worker.module.ts

@@ -0,0 +1,4 @@
+import { Module } from '@nestjs/common';
+
+@Module({})
+export class WorkerModule {}