feat: 集成 Artalk 自托管评论系统

- 新增 docs/overrides/partials/comments.html，Material 主题评论覆盖
- mkdocs.yml 添加 custom_dir: docs/overrides
- 首页添加 comments: false 关闭评论
- 新增 Artalk 部署文档（Docker + Nginx 反代 + 初始化指南）
- 技术 index 添加 Artalk 文档链接
- mkdocs.yml nav 添加 Artalk 评论系统入口

docs/overrides/partials/comments.html

@@ -0,0 +1,34 @@
+{#-
+  Artalk 评论系统集成
+  通过 Material 主题的 comments 块覆盖实现
+  如需关闭某页面的评论，在页面 frontmatter 中设置 comments: false
+-#}
+{% if page.meta.comments is not defined or page.meta.comments %}
+<div id="artalk-comments"></div>
+<link href="/artalk/dist/Artalk.css" rel="stylesheet">
+<script src="/artalk/dist/Artalk.js"></script>
+<script>
+document.addEventListener('DOMContentLoaded', function() {
+  var isDark = document.documentElement.getAttribute('data-md-color-scheme') === 'slate'
+
+  Artalk.init({
+    el:        '#artalk-comments',
+    site:      '我的知识库',
+    server:    window.location.origin + '/artalk',
+    pageKey:   window.location.pathname.replace(/\/$/, ''),
+    pageTitle: document.title,
+    darkMode:  isDark
+  })
+
+  // 跟随 MkDocs Material 深色模式切换
+  var observer = new MutationObserver(function(mutations) {
+    mutations.forEach(function(mutation) {
+      var scheme = document.documentElement.getAttribute('data-md-color-scheme')
+      var dark = scheme === 'slate'
+      if (Artalk.darkMode !== dark) Artalk.setDarkMode(dark)
+    })
+  })
+  observer.observe(document.documentElement, { attributes: true, attributeFilter: ['data-md-color-scheme'] })
+})
+</script>
+{% endif %}