feat: 新增全局侧边栏导航组件

src/components/Sidebar.astro

@@ -0,0 +1,19 @@
+---
+import { getCollection } from 'astro:content';
+// Astro v6 中获取所有文档
+const docs = await getCollection('docs');
+---
+<aside class="w-64 bg-gray-50 dark:bg-gray-800/30 border-r border-gray-200 dark:border-gray-800 h-screen sticky top-0 overflow-y-auto p-6 flex-shrink-0 hidden md:flex flex-col">
+  <div class="font-extrabold text-lg mb-6 text-gray-900 dark:text-white tracking-tight">📚 知识库导航</div>
+  <nav class="flex flex-col gap-1.5">
+    <a href="/" class="text-sm font-medium text-gray-600 dark:text-gray-400 hover:text-blue-600 dark:hover:text-blue-400 transition-colors px-2 py-1.5">
+      🏠 返回首页
+    </a>
+    <div class="my-2 border-t border-gray-200 dark:border-gray-700/50"></div>
+    {docs.map(doc => (
+      <a href={`/docs/${doc.id}`} class="text-sm text-gray-600 dark:text-gray-300 hover:text-blue-600 dark:hover:text-blue-400 hover:bg-gray-100 dark:hover:bg-gray-800 px-2 py-1.5 rounded-md transition-all truncate">
+        {doc.data.title || doc.id}
+      </a>
+    ))}
+  </nav>
+</aside>