fix: 修复示例URL显示错误并改进复制功能

- 将硬编码的示例URL改为动态生成，确保显示当前访问的域名/端口
- 修复复制功能在URL未加载时可能复制错误内容的问题
- 将url-preview字体从'Fira Code'改为通用monospace，提高兼容性

server.js

@@ -608,7 +608,7 @@ app.use(async (req, res) => {
         }
 
         .url-preview {
-            font-family: 'Fira Code', monospace;
+            font-family: monospace;
             background: #f1f5f9;
             padding: 0.75rem 1rem;
             border-radius: 8px;
@@ -635,6 +635,7 @@ app.use(async (req, res) => {
             color: var(--primary);
         }
 
+
         .features {
             display: grid;
             grid-template-columns: repeat(3, 1fr);
@@ -752,7 +753,7 @@ app.use(async (req, res) => {
             <div class="usage-row">
                 <span class="method-tag">GET</span>
                 <div class="url-preview">
-                    <span>${req.protocol}://${req.get('host')}/www.baidu.com</span>
+                    <span class="dynamic-url" data-path="/www.baidu.com">Loading...</span>
                     <button class="copy-btn" onclick="copyUrl(this)">复制</button>
                 </div>
             </div>
@@ -760,7 +761,7 @@ app.use(async (req, res) => {
             <div class="usage-row">
                 <span class="method-tag">GET</span>
                 <div class="url-preview">
-                    <span>${req.protocol}://${req.get('host')}/https://github.com</span>
+                    <span class="dynamic-url" data-path="/https://github.com">Loading...</span>
                     <button class="copy-btn" onclick="copyUrl(this)">复制</button>
                 </div>
             </div>
@@ -768,7 +769,7 @@ app.use(async (req, res) => {
             <div class="usage-row">
                 <span class="method-tag">GET</span>
                 <div class="url-preview">
-                    <span>${req.protocol}://${req.get('host')}/?url=www.baidu.com</span>
+                    <span class="dynamic-url" data-path="/?url=https://www.baidu.com">Loading...</span>
                     <button class="copy-btn" onclick="copyUrl(this)">复制</button>
                 </div>
             </div>
@@ -871,8 +872,19 @@ app.use(async (req, res) => {
     </footer>
 
     <script>
+        // 动态生成 URL，确保显示的是用户浏览器当前访问的地址（包含正确的域名/端口）
+        document.addEventListener('DOMContentLoaded', () => {
+            const origin = window.location.origin;
+            document.querySelectorAll('.dynamic-url').forEach(el => {
+                el.innerText = origin + el.getAttribute('data-path');
+            });
+        });
+
         function copyUrl(btn) {
-            const url = btn.previousElementSibling.innerText;
+            const urlSpan = btn.previousElementSibling;
+            const url = urlSpan.innerText;
+            if (url === 'Loading...') return;
+            
             navigator.clipboard.writeText(url).then(() => {
                 const originalText = btn.innerText;
                 btn.innerText = '已复制!';