improvement: error handeling structure changed and unified all across the app. user no longer sees inappropriate messages.

backend/src/main.ts

@@ -4,6 +4,10 @@ import { AppModule } from './app.module';
 import { ValidationPipe } from '@nestjs/common';
 import cookieParser from 'cookie-parser'; // 👈 Change this line!
 import { DocumentBuilder, SwaggerModule } from '@nestjs/swagger';
+import {
+  HttpExceptionFilter,
+  validationExceptionFactory,
+} from './common/errors';
 
 // At the VERY TOP of main.ts, before anything else
 const originalConsoleLog = console.log;
@@ -21,11 +25,14 @@ console.log = (...args) => {
 async function bootstrap() {
   const app = await NestFactory.create(AppModule);
   
+  app.useGlobalFilters(new HttpExceptionFilter());
+
   // Global pipes
   app.useGlobalPipes(new ValidationPipe({
     whitelist: true,
     forbidNonWhitelisted: true,
     transform: true,
+    exceptionFactory: validationExceptionFactory,
   }));
   
   // Cookie parser - this is correct for Express