feat: 代码块语法高亮 + 语言选择 + 样式统一

- 引入 @tiptap/extension-code-block-lowlight + lowlight 实现代码语法高亮
- 工具栏新增语言下拉选择器，光标在代码块内时显示，支持 27 种常用语言
- 默认语言 text，高亮主题适配 MetaLab 深蓝背景 (#1a2332)
- 代码块语言标签用 JS 动态注入 DOM 元素（避免 ::before 在 overflow 容器中失效）
- 详情页同步代码块高亮和语言标签显示
- 编辑器与详情页样式统一：代码块暗色背景、引用蓝色边框、链接 accent 蓝
- sanitizePolicy 放行 data-language 属性和 hljs-* class
- 修复 import map 避免 keyed plugin 重复实例
- 修复详情页代码块开头空白行（移除多余的 padding-top）
- 修复语法错误（多余的闭合括号）

templates/MetaLab-2026/html/posts/new.html

@@ -35,7 +35,7 @@
 
 /* 引用 */
 .tiptap blockquote {
-    border-left: 3px solid #e5e7eb;
+    border-left: 3px solid #3498db;
     padding-left: 1em;
     margin: 0.5em 0;
     color: #6b7280;
@@ -43,16 +43,17 @@
 
 /* 代码块 */
 .tiptap pre {
-    background: #1f2937;
-    color: #f3f4f6;
+    background: #1a2332;
+    color: #e2e8f0;
     padding: 12px 16px;
     border-radius: 6px;
     font-size: 13px;
     line-height: 1.5;
     overflow-x: auto;
     margin: 0.5em 0;
+    position: relative;
 }
-.tiptap pre code { background: transparent; padding: 0; color: inherit; font-size: inherit; }
+.tiptap pre code { background: transparent; padding: 0; color: inherit; font-size: inherit; white-space: pre; display: block; }
 .tiptap code {
     background: #f3f4f6;
     padding: 2px 5px;
@@ -60,6 +61,59 @@
     font-size: 0.9em;
     font-family: 'SF Mono', 'Menlo', 'Monaco', monospace;
 }
+/* 代码块语言标签 */
+.tiptap pre .code-lang-label {
+    position: absolute;
+    top: 0;
+    left: 0;
+    right: 0;
+    padding: 4px 16px;
+    font-size: 11px;
+    font-weight: 600;
+    color: #94a3b8;
+    background: #2c3e50;
+    border-radius: 6px 6px 0 0;
+    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Helvetica Neue', Arial, sans-serif;
+    pointer-events: none;
+    z-index: 1;
+}
+
+/* highlight.js 语法高亮主题 — 基于 One Dark，适配 MetaLab 深蓝背景 */
+.tiptap pre code .hljs-keyword,
+.tiptap pre code .hljs-selector-tag,
+.tiptap pre code .hljs-literal,
+.tiptap pre code .hljs-section,
+.tiptap pre code .hljs-link { color: #c792ea; }
+.tiptap pre code .hljs-string,
+.tiptap pre code .hljs-title,
+.tiptap pre code .hljs-name,
+.tiptap pre code .hljs-type,
+.tiptap pre code .hljs-attribute,
+.tiptap pre code .hljs-symbol,
+.tiptap pre code .hljs-bullet,
+.tiptap pre code .hljs-addition,
+.tiptap pre code .hljs-variable,
+.tiptap pre code .hljs-template-tag,
+.tiptap pre code .hljs-template-variable { color: #c3e88d; }
+.tiptap pre code .hljs-comment,
+.tiptap pre code .hljs-quote,
+.tiptap pre code .hljs-deletion,
+.tiptap pre code .hljs-meta { color: #676e95; }
+.tiptap pre code .hljs-number,
+.tiptap pre code .hljs-regexp,
+.tiptap pre code .hljs-built_in { color: #f78c6c; }
+.tiptap pre code .hljs-function .hljs-title,
+.tiptap pre code .hljs-doctag,
+.tiptap pre code .hljs-formula { color: #82aaff; }
+.tiptap pre code .hljs-tag,
+.tiptap pre code .hljs-subst { color: #f07178; }
+.tiptap pre code .hljs-emphasis { font-style: italic; }
+.tiptap pre code .hljs-strong { font-weight: bold; }
+.tiptap pre code .hljs-attr,
+.tiptap pre code .hljs-selector-attr,
+.tiptap pre code .hljs-selector-class,
+.tiptap pre code .hljs-selector-id,
+.tiptap pre code .hljs-selector-pseudo { color: #ffcb6b; }
 
 /* 水平线 */
 .tiptap hr { border: none; border-top: 1px solid #e5e7eb; margin: 1em 0; }
@@ -68,7 +122,7 @@
 .tiptap img { max-width: 100%; height: auto; border-radius: 6px; }
 
 /* 链接 */
-.tiptap a { color: #6366f1; text-decoration: underline; }
+.tiptap a { color: #3498db; text-decoration: underline; }
 
 /* Placeholder */
 .tiptap p.is-editor-empty:first-child::before {
@@ -104,7 +158,21 @@
     transition: background 0.15s;
 }
 .editor-toolbar button:hover { background: #e5e7eb; }
-.editor-toolbar button.is-active { background: #1f2937; color: #fff; }
+.editor-toolbar button.is-active { background: #1a2332; color: #fff; }
+.code-lang-select {
+    height: 30px;
+    padding: 0 6px;
+    border: 1px solid transparent;
+    border-radius: 4px;
+    background: transparent;
+    color: #374151;
+    font-size: 12px;
+    cursor: pointer;
+    font-family: inherit;
+    outline: none;
+}
+.code-lang-select:hover { border-color: #e5e7eb; }
+.code-lang-select:focus { border-color: #3498db; }
 .editor-toolbar .toolbar-divider {
     width: 1px;
     background: #e5e7eb;
@@ -143,6 +211,35 @@
             <button type="button" data-action="blockquote" title="引用">"</button>
             <span class="toolbar-divider"></span>
             <button type="button" data-action="codeBlock" title="代码块">{ }</button>
+            <select id="codeLangSelect" class="code-lang-select" style="display:none" title="选择语言">
+                <option value="text">text</option>
+                <option value="javascript">JavaScript</option>
+                <option value="typescript">TypeScript</option>
+                <option value="python">Python</option>
+                <option value="go">Go</option>
+                <option value="rust">Rust</option>
+                <option value="java">Java</option>
+                <option value="cpp">C++</option>
+                <option value="c">C</option>
+                <option value="csharp">C#</option>
+                <option value="ruby">Ruby</option>
+                <option value="php">PHP</option>
+                <option value="swift">Swift</option>
+                <option value="kotlin">Kotlin</option>
+                <option value="sql">SQL</option>
+                <option value="bash">Bash</option>
+                <option value="json">JSON</option>
+                <option value="yaml">YAML</option>
+                <option value="xml">XML</option>
+                <option value="css">CSS</option>
+                <option value="scss">SCSS</option>
+                <option value="html">HTML</option>
+                <option value="markdown">Markdown</option>
+                <option value="shell">Shell</option>
+                <option value="dockerfile">Dockerfile</option>
+                <option value="nginx">Nginx</option>
+                <option value="diff">Diff</option>
+            </select>
             <button type="button" data-action="horizontalRule" title="分隔线">—</button>
             <span class="toolbar-divider"></span>
             <button type="button" data-action="undo" title="撤销">↩</button>
@@ -170,6 +267,19 @@
 
 {{template "layout/footer.html" .}}
 
+<script type="importmap">
+{
+    "imports": {
+        "@tiptap/core": "https://esm.sh/@tiptap/core@3.13.0",
+        "@tiptap/starter-kit": "https://esm.sh/@tiptap/starter-kit@3.13.0",
+        "@tiptap/extension-placeholder": "https://esm.sh/@tiptap/extension-placeholder@3.13.0",
+        "@tiptap/extension-image": "https://esm.sh/@tiptap/extension-image@3.13.0",
+        "@tiptap/extension-code-block-lowlight": "https://esm.sh/@tiptap/extension-code-block-lowlight@3.13.0",
+        "lowlight": "https://esm.sh/lowlight@3.3.0",
+        "highlight.js/lib/languages/": "https://esm.sh/highlight.js@11.11.0/es/languages/"
+    }
+}
+</script>
 <script src="/static/js/common.js"></script>
 <script type="module" src="/static/js/editor.js"></script>
 </template>

templates/MetaLab-2026/html/posts/show.html

@@ -47,6 +47,20 @@
 
 <script src="/static/js/common.js"></script>
 <script>
+// ---- 代码块语言标签注入 ----
+(function() {
+    document.querySelectorAll('.post-detail-body pre').forEach(function(pre) {
+        var lang = pre.getAttribute('data-language');
+        if (lang) {
+            var label = document.createElement('div');
+            label.className = 'code-lang-label';
+            label.textContent = lang;
+            pre.insertBefore(label, pre.firstChild);
+            pre.style.paddingTop = '32px';
+        }
+    });
+})();
+
 (function() {
     var btn = document.getElementById('submitAuditBtn');
     if (!btn) return;