feat: 阿里云 MQTT 连接预设、连接分组与 MQTT 3.1.1 支持

- 后端引入 rumqttc v4 客户端，支持 MQTT 3.1.1 连接/发布/订阅，协议版本随连接下发
- 连接表单：阿里云预设管理（分组、导入导出、去抖自动保存），退出云模式需确认，mqtts 时端口跟随 8883
- 连接列表：分组列就地编辑（输入即创建），空分组提示优化
- 导入按内容去重并提示跳过数量，导出提示含明文密钥
- 调试日志密码脱敏；修复多处取消弹窗的 unhandled rejection

src-tauri/Cargo.lock

@@ -2248,6 +2248,7 @@ dependencies = [
 name = "mqttx"
 version = "0.1.0"
 dependencies = [
+ "rumqttc-v4-next",
  "rumqttc-v5-next",
  "serde",
  "serde_json",
@@ -3107,6 +3108,29 @@ dependencies = [
  "tokio-rustls",
 ]
 
+[[package]]
+name = "rumqttc-v4-next"
+version = "0.34.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b3767dde22a804ea806107d0f4331e33cb794d1b8468b11c86fb0c1366f07054"
+dependencies = [
+ "async-tungstenite",
+ "bytes",
+ "fixedbitset",
+ "flume",
+ "futures-util",
+ "log",
+ "mqttbytes-core-next",
+ "rumqttc-core-next",
+ "rustls-native-certs",
+ "rustls-pki-types",
+ "rustls-webpki",
+ "thiserror 2.0.20",
+ "tokio",
+ "tokio-rustls",
+ "tokio-util",
+]
+
 [[package]]
 name = "rumqttc-v5-next"
 version = "0.34.0"