feat：新增MQTT控制组件和自动告警系统

- 实现MQTT控制功能，处理水泵和灯光控制指令
- 新增土壤湿度和光照强度自动告警系统，阈值可配置
- 新建MQTT控制、自动告警和阈值管理相关文件
- 更新主应用，集成MQTT和自动控制功能
- 新增传感器数据与控制状态遥测上报
- 引入NVS和应用存储分区配置

components/mqtt_control/include/mqtt_control.h

@@ -0,0 +1,49 @@
+#pragma once
+
+#include <stdbool.h>
+
+#include "esp_err.h"
+#include "mqtt_client.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct {
+	bool has_mode;
+	bool auto_mode;
+
+	bool has_thresholds;
+	float soil_on_pct;
+	float soil_off_pct;
+	float light_on_lux;
+	float light_off_lux;
+
+	bool has_pump;
+	bool pump_on;
+
+	bool has_light;
+	bool light_on;
+} mqtt_control_command_t;
+
+typedef esp_err_t (*mqtt_control_command_handler_t)(const mqtt_control_command_t *cmd, void *user_ctx);
+
+esp_err_t mqtt_control_start(void);
+esp_err_t mqtt_control_stop(void);
+
+esp_err_t mqtt_control_register_command_handler(mqtt_control_command_handler_t handler, void *user_ctx);
+
+bool mqtt_control_is_connected(void);
+
+// Generic publish API for any topic.
+esp_err_t mqtt_control_publish(const char *topic,
+							   const char *payload,
+							   int qos,
+							   int retain);
+
+// Publish telemetry payload to default sensor topic.
+esp_err_t mqtt_control_publish_sensor(const char *payload, int qos, int retain);
+
+#ifdef __cplusplus
+}
+#endif