添加 Next.js Web 应用

- 创建 Next.js + TypeScript + Tailwind CSS Web 应用
- 支持 Markdown 渲染和 GFM 格式
- 支持 Obsidian 风格 wiki 链接 [[Page|Label]]
- 侧边栏导航，按分类组织页面
- 图片资源支持（通过 API 路由从 wiki/assets 提供）
- 响应式设计
- 更新 README 添加 Web 应用使用说明

web/components/Sidebar.tsx

@@ -0,0 +1,77 @@
+import Link from "next/link";
+import { getCategories, type WikiPage } from "@/lib/wiki";
+
+interface SidebarProps {
+  pages: WikiPage[];
+  currentSlug?: string;
+}
+
+export function Sidebar({ pages, currentSlug }: SidebarProps) {
+  const categories = getCategories(pages);
+  const rootPages = pages.filter((p) => !p.category);
+
+  return (
+    <div className="bg-white rounded-lg shadow-sm p-4 sticky top-24">
+      <h2 className="text-lg font-semibold mb-4 text-gray-900">
+        知识库导航
+      </h2>
+
+      {/* Categories */}
+      {categories.length > 0 && (
+        <div className="mb-6">
+          <h3 className="text-sm font-medium text-gray-500 mb-2">分类</h3>
+          <ul className="space-y-2">
+            {categories.map((cat) => (
+              <li key={cat}>
+                <span className="text-sm font-medium text-gray-700 capitalize">
+                  {cat}
+                </span>
+                <ul className="ml-3 mt-1 space-y-1">
+                  {pages
+                    .filter((p) => p.category === cat)
+                    .map((page) => (
+                      <li key={page.slug}>
+                        <Link
+                          href={`/wiki/${page.slug}`}
+                          className={`text-sm block py-0.5 ${
+                            page.slug === currentSlug
+                              ? "text-blue-700 font-semibold"
+                              : "text-blue-600 hover:text-blue-800 hover:underline"
+                          }`}
+                        >
+                          {page.title}
+                        </Link>
+                      </li>
+                    ))}
+                </ul>
+              </li>
+            ))}
+          </ul>
+        </div>
+      )}
+
+      {/* Root pages */}
+      {rootPages.length > 0 && (
+        <div>
+          <h3 className="text-sm font-medium text-gray-500 mb-2">其他页面</h3>
+          <ul className="space-y-1">
+            {rootPages.map((page) => (
+              <li key={page.slug}>
+                <Link
+                  href={page.slug === "INDEX" ? "/" : `/wiki/${page.slug}`}
+                  className={`text-sm block py-0.5 ${
+                    (currentSlug === page.slug || (!currentSlug && page.slug === "INDEX"))
+                      ? "text-blue-700 font-semibold"
+                      : "text-blue-600 hover:text-blue-800 hover:underline"
+                  }`}
+                >
+                  {page.title}
+                </Link>
+              </li>
+            ))}
+          </ul>
+        </div>
+      )}
+    </div>
+  );
+}