fix: 注册 /v1/common/client/download 路由，修复客户端下载链接 404

handler 和 logic 代码已迁移但 routes.go 漏注册该端点。

Co-Authored-By: claude-flow <ruv@ruv.net>

internal/handler/routes.go

@@ -716,6 +716,9 @@ func RegisterHandlers(router *gin.Engine, serverCtx *svc.ServiceContext) {
 		// Get Client
 		commonGroupRouter.GET("/client", common.GetClientHandler(serverCtx))
 
+		// Get Download Link
+		commonGroupRouter.GET("/client/download", common.GetDownloadLinkHandler(serverCtx))
+
 		// Heartbeat
 		commonGroupRouter.GET("/heartbeat", common.HeartbeatHandler(serverCtx))