refactor: unify SimpleLed via embedded-hal, remove Option<L> from BoardParts

- Added embedded-hal 1.0 as direct dep (already transitive via embedded-hal-async)
- SimpleLed<P: OutputPin> now generic over any HAL — single definition in driver/
- Removed duplicate SimpleLed from board/esp32s3.rs and board/wio_tracker_l1.rs
- Changed BoardParts.led from Option<L> to L — boards with no LED use ()
- Display task calls led.set_rgb() unconditionally (no-op for () boards)
- RAK board: led: () instead of led: None

src/board/esp32s3.rs

@@ -18,20 +18,6 @@ use crate::hal::esp32s3 as mcu;
 
 pub use mcu::{I2cBus as DisplayI2c, SpiBus};
 
-// ── LED driver ──────────────────────────────────────────────────────
-
-pub struct SimpleLed(pub Output<'static>);
-
-impl super::traits::RgbLed for SimpleLed {
-    async fn set_rgb(&mut self, r: u8, g: u8, b: u8) {
-        if r > 0 || g > 0 || b > 0 {
-            self.0.set_high();
-        } else {
-            self.0.set_low();
-        }
-    }
-}
-
 // ── Concrete peripheral types ───────────────────────────────────────
 
 type Nss = Output<'static>;