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>

server/internal/tenant/transport/router.go

@@ -249,7 +249,7 @@ func RegisterRoutes(app *bootstrap.App) {
 
 	if swagger.EnabledForMode(app.Config.Server.Mode) {
 		swagger.Register(app.Engine, swagger.Config{
-			Title:   "Geo Rankly Admin API",
+			Title:   "省心推 Admin API",
 			Version: "dev",
 		})
 	}