feat(frontend): Update better-auth, add orga slug check, add PDF preview, fix invitation

legalconsenthub/composables/useBetterAuth.ts

@@ -6,6 +6,12 @@ export function useBetterAuth() {
   const { organization } = useAuth()
 
   async function createOrganization(name: string, slug: string, logo?: string) {
+    const slugCheck = await organization.checkSlug({ slug })
+    if (!slugCheck.data.available) {
+      toast.add({ title: 'Slug bereits vergeben', description: 'Bitte wählen Sie einen anderen Slug', color: 'error' })
+      return Promise.reject()
+    }
+
     await organization.create(
       { name, slug, logo },
       {