fix(a11y): 无障碍与 lint 修复（对比度/alt 属性/触控目标收窄）+ Geist 本地字体系统

src/components/sections/insight-card.test.tsx

@@ -75,9 +75,11 @@ describe('InsightCard', () => {
     const { container } = render(
       <InsightCard {...mockInsight} featured image="/images/insights/trends.jpg" />
     );
-    const img = container.querySelector('img');
-    expect(img).toBeInTheDocument();
-    expect(img).toHaveAttribute('src', '/images/insights/trends.jpg');
+    // 组件用 CSS 背景图而非 <img>，使 404 图片静默降级为纯色底
+    const bg = container.querySelector('[style*="background-image"]');
+    expect(bg).toBeInTheDocument();
+    expect(bg).toHaveAttribute('aria-hidden', 'true');
+    expect(bg).toHaveStyle({ backgroundImage: 'url(/images/insights/trends.jpg)' });
   });
 
   it('should render link element when provided', async () => {