fix(i18n): drop the duplicate zh-CN Attach key (#606 merge-time fix)

ZH_CN already had `Attach: '附加'` (the tile grid's and remote discovery's
Attach buttons). #606 added a second `Attach: '添加附件'` later in the same
object literal, which won and turned every Attach into "add attachment".
The duplicate is removed; 附加 covers the phone toolbar button too.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/web/public/i18n.js

@@ -677,7 +677,6 @@
     // placeholder and label are looked up by the module at build time, since
     // the DOM translator skips <textarea> subtrees.
     'Compose prompt': '撰写提示词',
-    Attach: '添加附件',
     'Open a session to attach a file': '请先打开一个会话再添加附件',
     'Only image or video files are supported': '仅支持图片或视频文件',
     'Compose prompt, draft saved': '撰写提示词，草稿已保存',