feat: 创作中心内容管理页 - 锁定文章显示"已锁定"标签，隐藏编辑按钮

- 文章被锁定时，在主状态徽章旁追加"已锁定"标签（如 "已发布" "已锁定"）
- 被锁定的帖子隐藏"编辑"按钮，仅显示"查看"和"删除"按钮
- API 层已有保护：Update 方法检查 IsLocked，拒绝越权编辑

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

@@ -39,6 +39,7 @@
                     <a href="/posts/{{.ID}}" class="post-item-title" target="_blank">{{.Title}}</a>
                     <div class="post-item-meta">
                         <span class="post-status-badge status-{{.Status}}">{{index $.StatusNames .Status}}</span>
+                        {{if .IsLocked}}<span class="post-status-badge status-locked">已锁定</span>{{end}}
                         <span>{{.CreatedAt.Format "2006-01-02 15:04"}}</span>
                         {{if .RejectReason}}
                         <span class="post-reject-hint">退回理由：{{.RejectReason}}</span>
@@ -46,7 +47,7 @@
                     </div>
                 </div>
                 <div class="post-item-actions">
-                    <a href="/studio/write?id={{.ID}}" class="action-btn">编辑</a>
+                    {{if not .IsLocked}}<a href="/studio/write?id={{.ID}}" class="action-btn">编辑</a>{{end}}
                     <a href="/posts/{{.ID}}" target="_blank" class="action-btn">查看</a>
                     <button class="action-btn danger" onclick="deletePost({{.ID}})" title="删除">删除</button>
                 </div>