Add run limit feature for relay channels with NVS support

- Introduced configuration options for enabling run limits in Kconfig.
- Added APIs to get and set run limits for individual relay channels.
- Implemented run limit timer functionality to automatically stop channels.
- Updated NVS handling to store and retrieve run limit values.
- Enhanced documentation in README and code comments to reflect new feature.

Closes #1080

include/relay_chn_adapter.h

@@ -101,6 +101,36 @@ static inline relay_chn_direction_t relay_chn_get_direction(uint8_t chn_id)
     return relay_chn_ctl_get_direction(chn_id);
 }
 
+#if RELAY_CHN_ENABLE_RUN_LIMIT == 1
+/**
+ * @brief Get the run limit for the specified channel
+ *
+ * @param chn_id The ID of the relay channel to query.
+ * 
+ * @return The run limit value for the relevant channel if the channel ID is valid.
+ *         0 if the channel ID is invalid.
+ */
+extern uint16_t relay_chn_ctl_get_run_limit(uint8_t chn_id);
+
+/**
+ * @brief Set the run limit for the specified channel
+ *
+ * @param chn_id The ID of the relay channel to query.
+ * @param time_sec The run limit time in seconds.
+ */
+extern void relay_chn_ctl_set_run_limit(uint8_t chn_id, uint16_t time_sec);
+
+static inline uint16_t relay_chn_get_run_limit(uint8_t chn_id)
+{
+    return relay_chn_ctl_get_run_limit(chn_id);
+}
+
+static inline void relay_chn_set_run_limit(uint8_t chn_id, uint16_t time_sec)
+{
+    relay_chn_ctl_set_run_limit(chn_id, time_sec);
+}
+#endif // RELAY_CHN_ENABLE_RUN_LIMIT == 1
+
 #else
 
 /**
@@ -179,6 +209,32 @@ static inline relay_chn_direction_t relay_chn_get_direction(void)
     return relay_chn_ctl_get_direction();
 }
 
+#if RELAY_CHN_ENABLE_RUN_LIMIT == 1
+/**
+ * @brief Get the run limit for the channel
+ * 
+ * @return The run limit value for the channel.
+ */
+extern uint16_t relay_chn_ctl_get_run_limit(void);
+
+/**
+ * @brief Set the run limit for the channel
+ *
+ * @param time_sec The run limit time in seconds.
+ */
+extern void relay_chn_ctl_set_run_limit(uint16_t time_sec);
+
+static inline uint16_t relay_chn_get_run_limit(void)
+{
+    return relay_chn_ctl_get_run_limit();
+}
+
+static inline void relay_chn_set_run_limit(uint16_t time_sec)
+{
+    relay_chn_ctl_set_run_limit(time_sec);
+}
+#endif // RELAY_CHN_ENABLE_RUN_LIMIT == 1
+
 #endif // RELAY_CHN_COUNT > 1
 
 #ifdef __cplusplus