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/rak_wisblock_4631.rs

@@ -137,7 +137,7 @@ impl LoRaBoard for Board {
             radio,
             host,
             display,
-            led: None,
+            led: (),
             mac: Self::mac_address(),
         }
     }