fix: resolve ambiguous '추가' button in E2E tests (#917)

adminfront/tests/users.spec.ts

@@ -721,7 +721,7 @@ test.describe("User Management", () => {
     await expect(page.locator("input#department")).toHaveCount(0);
 
     await expect(page.getByText(/대표 소속/i)).toHaveCount(0);
-    await page.getByRole("button", { name: /^추가$/i }).click();
+    await page.getByTestId("add-appointment-btn").click();
     await expect(page.getByTestId("appointment-row-0")).toBeVisible();
     await expect(
       page.getByTestId("appointment-tenant-owner-line-0"),