feat: initialize NestJS application with global error handling and response standardization

- Added nest-cli.json for NestJS configuration.
- Created package.json with dependencies and scripts for building, testing, and linting.
- Implemented AppController and AppService with a basic "Hello World!" response.
- Introduced ContextModule and ContextService for managing request-scoped context.
- Developed custom decorators for response messages and standardized error handling.
- Created global exception filter to handle various error types and format responses.
- Implemented response standardization interceptor to wrap successful responses.
- Added middleware for generating unique request IDs.
- Established DTOs for API responses and error handling.
- Configured TypeScript settings for the project.
- Set up Jest for testing with end-to-end test cases.

src/main.ts

@@ -0,0 +1,38 @@
+import { HttpAdapterHost, NestFactory } from '@nestjs/core';
+import { AppModule } from './app.module';
+import { ValidationPipe } from '@nestjs/common';
+import { AllExceptionsFilter } from './common/filters/all-exceptions.filter';
+import { ContextService } from './common/context/context.service';
+
+async function bootstrap() {
+  const app = await NestFactory.create(AppModule);
+
+  // --- 1. Enable Global Validation Pipe ---
+  // This is part of Feature #5, but required for the filter to catch
+  // class-validator errors.
+  app.useGlobalPipes(
+    new ValidationPipe({
+      whitelist: true, // Strip properties not in DTO
+      transform: true, // Automatically transform payloads to DTO instances
+      forbidNonWhitelisted: true, // Throw error on non-whitelisted properties
+      transformOptions: {
+        enableImplicitConversion: true, // Convert query/path params
+      },
+    }),
+  );
+
+  // --- 2. Register Global Exception Filter ---
+  // We MUST get these dependencies from the app instance
+  // *after* it has been created.
+  const httpAdapterHost = app.get(HttpAdapterHost);
+  const contextService = app.get(ContextService);
+  app.useGlobalFilters(
+    new AllExceptionsFilter(httpAdapterHost, contextService),
+  );
+  // Note: We are instantiating it here instead of using APP_FILTER
+  // because the filter *depends* on other providers (HttpAdapterHost)
+  // that are only available *after* the app is created.
+
+  await app.listen(process.env.PORT ?? 3000);
+}
+bootstrap();