FEAT: Implement deceased/givenaway enclosure visibility rules, preserve external clan name, and hide receiver fields for deceased gerbils

gerbil-manager-web/src/pages/VertragWizardPage.tsx

@@ -47,7 +47,7 @@ export default function VertragWizardPage() {
   const [newContact, setNewContact] = useState({ name: '', email: '', phone: '', address: '' })
 
   const contacts = useApi(() => listContactsPaged({ page: 1, pageSize: 1000, orderBy: 'name' }), [])
-  const contactItems = useMemo(() => contacts.data?.items ?? [], [contacts.data])
+  const contactItems = useMemo(() => (contacts.data?.items ?? []).filter((c) => c.isReceiver), [contacts.data])
   const filteredContacts = useMemo(() => {
     const needle = contactSearch.trim().toLowerCase()
     return needle === ''
@@ -62,6 +62,8 @@ export default function VertragWizardPage() {
       email: newContact.email.trim() || null,
       phone: newContact.phone.trim() || null,
       address: newContact.address.trim() || null,
+      isReceiver: true,
+      isBreeder: false,
     }),
   )
   async function onCreateContact() {