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/traits.rs

@@ -56,6 +56,6 @@ pub struct BoardParts<R, C, D, L> {
     pub radio: R,
     pub host: C,
     pub display: Option<D>,
-    pub led: Option<L>,
+    pub led: L,
     pub mac: [u8; 6],
 }