refactor: LoRaBoard trait with full associated types + BoardParts

- LoRaBoard trait now has associated types: RadioParts, CommParts, DisplayParts, DisplayDriver
- into_parts() is on the trait (enforced by compiler, not implicit convention)
- BoardParts<R, C, D> struct replaces tuple return from into_parts()
- mac_address() stays on trait, MAC also in BoardParts for convenience
- Removed mac field from DisplayParts (display task calls Board::mac_address())
- DisplayDriver associated type requires DrawTarget<Color = BinaryColor>

src/board/esp32s3.rs

@@ -44,7 +44,6 @@ pub struct UartParts {
 
 pub struct DisplayParts {
     pub i2c: DisplayI2c,
-    pub mac: [u8; 6],
 }
 
 // ── Display driver ──────────────────────────────────────────────────