make async can useable

rust/src/hal/v4_hal.rs

@@ -297,7 +297,7 @@ pub(crate) async fn create_v4(
     Ok(Box::new(v))
 }
 
-#[async_trait]
+#[async_trait(?Send)]
 impl<'a> BoardInteraction<'a> for V4<'a> {
     fn get_tank_sensor(&mut self) -> Result<&mut TankSensor<'a>, FatError> {
         Ok(&mut self.tank_sensor)
@@ -461,7 +461,6 @@ impl<'a> BoardInteraction<'a> for V4<'a> {
 
     async fn detect_sensors(&mut self) -> Result<alloc::string::String, FatError> {
         // Delegate to sensor autodetect and build JSON
-        use alloc::string::ToString;
         let detected = self.sensor.autodetect().await?;
         // Build JSON manually to avoid exposing internal types
         let mut s = alloc::string::String::from("{\"plants\":[");