fix(03): strip TLD from domaincheck input before sending to API

Users naturally type full domains (e.g. "google.de") but the API
validates DNS labels only. Extract the label part before the first
dot to prevent 400 validation errors.

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

apps/web/src/app/(portal)/modules/domaincheck/components/DomainInput.tsx

@@ -20,9 +20,9 @@ export function DomainInput({ onSubmit, isLoading }: DomainInputProps) {
 
   const handleSubmit = (e: FormEvent) => {
     e.preventDefault();
-    const trimmed = domain.trim();
-    if (trimmed) {
-      onSubmit(trimmed);
+    const label = domain.trim().split('.')[0];
+    if (label) {
+      onSubmit(label);
     }
   };