docs: 调整导航菜单中备用地址的位置和文案

将“备用地址”菜单项重命名为“unibest备用地址”并调整到“相关链接”下方
更新菜单项中文案，将“首选”改为“本站”，“备选”改为“备用”

docs/.vitepress/config.mts

@@ -120,17 +120,17 @@ export default defineConfig({
         text: '更新日志',
         link: '/changelog/CHANGELOG',
       },
-      {
-        text: '备用地址',
-        items: [
-          { text: 'unibest.tech(首选)', link: 'https://unibest.tech' },
-          { text: 'github page(备选)', link: 'https://feige996.github.io/unibest/' },
-        ],
-      },
       {
         text: '相关链接',
         link: '/other/links/links',
       },
+      {
+        text: 'unibest备用地址',
+        items: [
+          { text: 'unibest.tech(本站)', link: 'https://unibest.tech' },
+          { text: 'github page(备用)', link: 'https://feige996.github.io/unibest/' },
+        ],
+      },
     ],
     sidebar: [
       {