feat: Add 批改心法課程 link to header navigation

- Add Google Drive course materials link to header
- Add special styling with 📚 icon and green gradient
- Link opens in new tab for easy access to course materials
- Positioned after API docs in navigation bar

frontend/src/App.css

@@ -148,6 +148,24 @@ body {
   box-shadow: 0 6px 20px rgba(238, 90, 36, 0.4);
 }
 
+.nav-link.course-link {
+  background: linear-gradient(135deg, #10ac84, #00d2d3);
+  box-shadow: 0 4px 15px rgba(16, 172, 132, 0.3);
+  position: relative;
+  overflow: hidden;
+}
+
+.nav-link.course-link:hover {
+  background: linear-gradient(135deg, #00d2d3, #10ac84);
+  box-shadow: 0 6px 20px rgba(16, 172, 132, 0.4);
+  transform: translateY(-2px);
+}
+
+.nav-link.course-link::before {
+  content: '📚';
+  margin-right: 0.5rem;
+}
+
 .app-header p {
   font-size: 1.1rem;
   color: #64748b;

frontend/src/App.tsx

@@ -190,6 +190,14 @@ function App() {
             >
               API 文檔
             </a>
+            <a 
+              href="https://drive.google.com/drive/folders/1jFNx3loIJtEo8CwkendtpGh6m8WMa_QH" 
+              target="_blank" 
+              rel="noopener noreferrer"
+              className="nav-link course-link"
+            >
+              批改心法課程
+            </a>
           </nav>
         </div>
         <div className="header-controls">