🐛 fix(update): 恢复检查更新按钮加载动效

- 为设置中心加载图标恢复持续旋转
- 保留其他界面的减少动态效果策略
- 补充 reduced-motion 样式回归测试

frontend/src/App.css

@@ -3036,6 +3036,12 @@ body[data-theme='dark'] .gonavi-settings-center-entry:hover {
     animation-duration: 0.01ms !important;
     animation-iteration-count: 1 !important;
   }
+
+  /* Loading indicators communicate ongoing work, rather than decorative motion. */
+  .gonavi-settings-center-modal .ant-btn-loading-icon .anticon-spin {
+    animation-duration: 1s !important;
+    animation-iteration-count: infinite !important;
+  }
 }
 
 .gonavi-ai-settings-nav-description {

frontend/src/App.tool-center.test.ts

@@ -6,6 +6,10 @@ const appSource = readFileSync(
   fileURLToPath(new globalThis.URL('./App.tsx', import.meta.url)),
   'utf8',
 );
+const appCss = readFileSync(
+  fileURLToPath(new globalThis.URL('./App.css', import.meta.url)),
+  'utf8',
+);
 
 describe('settings center tool entries', () => {
 
@@ -25,4 +29,10 @@ describe('settings center tool entries', () => {
     const minimiseProbeIndex = resizeHandlerSource.indexOf('rememberMinimisedStateSoon();');
     const dprCheckIndex = resizeHandlerSource.indexOf("scheduleDevicePixelRatioCheck('resize');");
   });
+
+  it('keeps button loading indicators animated when reduced motion is enabled', () => {
+    expect(appCss).toMatch(
+      /@media \(prefers-reduced-motion: reduce\) \{[\s\S]*?\.gonavi-settings-center-modal \.ant-btn-loading-icon \.anticon-spin \{[^}]*animation-duration: 1s !important;[^}]*animation-iteration-count: infinite !important;[^}]*\}/,
+    );
+  });
 });