Fix five confirmed bugs: typo, field name, auth, success message, debug print

- Fix `fist_name` typo in CSV bulk upload (first_name was always None)
- Fix CSV file field name mismatch: `members_data` → `csv_file` (matches form + template)
- Add `@login_required` to backend index view (was unprotected)
- Move `messages.success` inside `if form.is_valid()` (was always shown)
- Remove debug `print(response.headers)` from HTMXViewMixin

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/views.py

@@ -15,6 +15,7 @@ from backend.forms import ConfigurationForm
 
 
 # Create your views here.
+@login_required
 def index(request):
     return render(request, "backend/index.html")
 
@@ -54,6 +55,6 @@ def configuration(request: HttpRequest) -> HttpResponse:
             Switch.objects.bulk_update(switches.values(), ["active"])
             cache.clear()
 
-        messages.success(request=request, message=_("Settings have been saved successfully"))
+            messages.success(request=request, message=_("Settings have been saved successfully"))
 
     return render(request, "backend/configuration.html", {"form": form})