feat: Initial authentication logic and UX

wp-content/themes/moonshine/app/composables/useAuth.ts

@@ -0,0 +1,6 @@
+export function useAuth() {
+  const { loggedIn: isLoggedIn, session } = useUserSession();
+  const hasRole = (role: string) => session.value?.user?.roles?.includes(role) || false;
+  const isAdmin = computed(() => hasRole("administrator"));
+  return { isLoggedIn, hasRole, isAdmin };
+}