fix: add missing required user fields in bulk register

backend/main.py

@@ -270,7 +270,11 @@ async def bulk_register_students(file: UploadFile = File(...), session: Session
             phone=phone,
             password_hash=hashed_password,
             target_exam=exam,
-            tier=tier
+            tier=tier,
+            student_class=models.ClassEnum.TWELFTH,
+            medium=models.MediumEnum.ENGLISH,
+            city="Unknown",
+            state="Unknown"
         )
         session.add(user)
         results.append({