refactor(auth): simplify user registration process by removing rollback logic

- Eliminated the rollback logic for user creation in the registration process, streamlining the function and reducing complexity.
- Maintained error handling for existing email addresses while ensuring activation emails are sent without exposing user details.

backend/services/authService.js

@@ -7,10 +7,9 @@ import { sendActivationEmail } from './emailService.js';
 import { devLog, errorLog } from '../utils/logger.js';
 
 const register = async (email, password) => {
-  let createdUser = null;
   try {
     const activationCode = Math.random().toString(36).substring(2, 15);
-    createdUser = await User.create({ email, password, activationCode });
+    await User.create({ email, password, activationCode });
 
     // Aktivierungs‑E-Mail versenden
     await sendActivationEmail(email, activationCode);
@@ -29,16 +28,6 @@ const register = async (email, password) => {
     // Optional zusätzlich ausführlich im Dev-Log
     devLog('[authService.register] Stacktrace:', error?.stack);
 
-    // 2) Falls User bereits angelegt wurde, wieder löschen (Rollback)
-    if (createdUser) {
-      try {
-        await createdUser.destroy();
-        devLog(`[authService.register] Angelegten User (id=${createdUser.id}, email=${createdUser.email}) wegen Fehler wieder gelöscht`);
-      } catch (cleanupError) {
-        devLog('[authService.register] Konnte angelegten User nach Fehler nicht löschen', cleanupError);
-      }
-    }
-
     // E-Mail existiert bereits
     if (error.name === 'SequelizeUniqueConstraintError') {
       const err = new Error('E-Mail-Adresse wird bereits verwendet');