feat(docs): add local search to Docusaurus site

Add @easyops-cn/docusaurus-search-local (v0.55.1) for offline/local
full-text search across all documentation pages.

- Search bar appears in the navbar (Ctrl/Cmd+K shortcut)
- Builds a search index at build time — no external service needed
- Highlights matched terms on target page after clicking a result
- Dedicated /search page for expanded results
- Blog indexing disabled (blog is off)
- docsRouteBasePath set to '/' to match existing docs routing

website/docusaurus.config.ts

@@ -26,6 +26,20 @@ const config: Config = {
     locales: ['en'],
   },
 
+  themes: [
+    [
+      require.resolve('@easyops-cn/docusaurus-search-local'),
+      /** @type {import("@easyops-cn/docusaurus-search-local").PluginOptions} */
+      ({
+        hashed: true,
+        language: ['en'],
+        indexBlog: false,
+        docsRouteBasePath: '/',
+        highlightSearchTermsOnTargetPage: true,
+      }),
+    ],
+  ],
+
   presets: [
     [
       'classic',