feat(shell): Add commands for valve timing

- Add shell commands 'valve set_open_time' and 'valve set_close_time' to configure the virtual valve.
- Extend the 'show_config' command to display the new timing values.
- The new settings are persisted to flash storage.

software/apps/slave_node/src/main.c

@@ -238,6 +238,28 @@ uint8_t modbus_get_unit_id(void)
 	return server_param.server.unit_id;
 }
 
+void valve_set_max_open_time(uint16_t seconds)
+{
+    max_opening_time_s = seconds;
+    settings_save_one("valve/max_open_time", &max_opening_time_s, sizeof(max_opening_time_s));
+}
+
+void valve_set_max_close_time(uint16_t seconds)
+{
+    max_closing_time_s = seconds;
+    settings_save_one("valve/max_close_time", &max_closing_time_s, sizeof(max_closing_time_s));
+}
+
+uint16_t valve_get_max_open_time(void)
+{
+    return max_opening_time_s;
+}
+
+uint16_t valve_get_max_close_time(void)
+{
+    return max_closing_time_s;
+}
+
 static int settings_load_cb(const char *name, size_t len,
                                 settings_read_cb read_cb, void *cb_arg)
 {