feat(admin): groups management UI in the console

Add a super-admin-only Groups tab to create, edit and delete groups
(name, admin ids, owner scope). Routes now require a group via a select
in the editor, group names are shown on route cards, and the new
useMe/useGroups composables back the UI.

admin/composables/useMe.ts

@@ -0,0 +1,30 @@
+import type { Me } from "~/types";
+
+export function useMeApi() {
+  const me = ref<Me | null>(null);
+  const loading = ref(false);
+  const needLogin = ref(false);
+
+  async function load(): Promise<void> {
+    loading.value = true;
+    needLogin.value = false;
+    try {
+      const res = await fetch("/admin/api/me", {
+        headers: { accept: "application/json" },
+        credentials: "same-origin",
+      });
+      if (res.status === 401) {
+        needLogin.value = true;
+        return;
+      }
+      if (!res.ok) throw new Error(`HTTP ${res.status}`);
+      me.value = (await res.json()) as Me;
+    } catch {
+      me.value = null;
+    } finally {
+      loading.value = false;
+    }
+  }
+
+  return { me, loading, needLogin, load };
+}