Fix link copy toast messages, remove custom toast in favor of authStore, remove a component that was no longer used.

frontend/src/admin/AdminUserDetail.vue

@@ -35,7 +35,7 @@ const backButtonRef = ref(null)
 const hasActiveModal = computed(() => props.showRegModal)
 
 function onLinkCopied() {
-  authStore.showMessage('Link copied to clipboard!')
+  authStore.showMessage(`📋 Link copied! Send it to ${props.selectedUser.display_name}.`)
 }
 
 function handleEditName() {