fix: batch-uninstall 也检查 SSHKey(对齐 batch-upgrade 逻辑)

backend/internal/api/handlers/agent_install.go

@@ -357,7 +357,7 @@ func (h *AgentInstallHandler) BatchUninstallAgent(c *gin.Context) {
 				log.Printf("[BatchUninstall] 服务器 %d 不存在，跳过", id)
 				continue
 			}
-			if server.Username == "" || server.Password == "" {
+			if server.Username == "" || (server.Password == "" && server.SSHKey == "") {
 				h.db.Model(&server).Updates(map[string]interface{}{"agent_status": "offline", "agent_version": ""})
 				log.Printf("[BatchUninstall] %s 无SSH凭据，已标记离线", server.Hostname)
 				successCount++