Implement health check service and global exception handling

backend/src/main.ts

@@ -1,11 +1,16 @@
 import { ValidationPipe } from '@nestjs/common';
 import { NestFactory } from '@nestjs/core';
 import { AppModule } from './app.module';
+import { GlobalExceptionFilter } from './common/filters/global-exception.filter';
 
 async function bootstrap() {
   const app = await NestFactory.create(AppModule);
 
   app.setGlobalPrefix('api');
+  
+  // Registrera global exception filter
+  app.useGlobalFilters(new GlobalExceptionFilter());
+  
   app.useGlobalPipes(
     new ValidationPipe({
       whitelist: true,