chore: rebrand product as 省心推 and lock UI to zh-CN

Update server titles, web/desktop window/tray/document titles, login
copy, and electron build metadata to use the Chinese product name 省心推.
Drop the runtime locale switcher and en-US import — the app now ships
zh-CN only.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop-client/package.json

@@ -2,10 +2,11 @@
   "name": "@geo/desktop-client",
   "version": "0.1.0",
   "private": true,
-  "description": "GEO Rankly Desktop — account health, monitor scheduler, and publish dispatch client.",
+  "description": "省心推客户端 — 连接和管理您的媒体账号，轻松发布和监控内容表现。",
   "author": {
-    "name": "GEO Rankly",
-    "email": "support@geo-rankly.local"
+    "name": "Liang Xu",
+    "email": "liangxu@qq.com",
+    "url": "https://shengxintui.com"
   },
   "type": "module",
   "main": "out/main/bootstrap.cjs",