Remove unused imports and variables (S1128, S1481, S1854)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/components/ModalHeader.test.js

@@ -3,7 +3,7 @@
 // Authors:
 //   imacat.yang@dsp.im (imacat), 2026/03/05
 
-import { describe, it, expect, beforeEach, vi } from "vitest";
+import { describe, it, expect, beforeEach } from "vitest";
 import { mount } from "@vue/test-utils";
 import { setActivePinia, createPinia } from "pinia";
 import ModalHeader from "@/views/AccountManagement/ModalHeader.vue";