fix: V4 also has plain LED on GPIO35, not WS2812 on GPIO38

Per the official V4 schematic (HTIT-WB32LAF_V4.3.pdf), the V4 has
an orange LED on GPIO35 with a series resistor — same setup as V3.
GPIO38 is GNSS_RX on V4, not an LED. Neither V3 nor V4 has a WS2812.

- V4: switched from WS2812/GPIO38 to SimpleLed/GPIO35
- Removed ws2812.rs driver (no current board uses addressable LEDs)
- All ESP boards now use the same SimpleLed driver on GPIO35

src/board/heltec_v4.rs

@@ -1,11 +1,9 @@
 use esp_hal::gpio::{Level, Output, OutputConfig};
-use esp_hal::rmt::{Rmt, TxChannelConfig, TxChannelCreator};
-use esp_hal::time::Rate;
 use static_cell::StaticCell;
 
 use super::esp32s3;
 use super::traits::{BoardParts, LoRaBoard};
-use crate::driver::ws2812::Ws2812;
+use crate::driver::simple_led::SimpleLed;
 use crate::hal::esp32s3 as mcu;
 
 pub use super::esp32s3::{
@@ -14,7 +12,7 @@ pub use super::esp32s3::{
 
 pub type UsbDriver = esp_hal::otg_fs::asynch::Driver<'static>;
 
-pub type LedDriver = Ws2812;
+pub type LedDriver = SimpleLed;
 
 pub struct UsbParts {
     pub driver: UsbDriver,
@@ -32,7 +30,7 @@ impl LoRaBoard for Board {
     type CommParts = UsbParts;
     type DisplayParts = DisplayParts;
     type DisplayDriver = DisplayDriver;
-    type LedDriver = Ws2812;
+    type LedDriver = LedDriver;
 
     fn init() -> Self {
         let p = esp_hal::init(esp_hal::Config::default());
@@ -43,7 +41,7 @@ impl LoRaBoard for Board {
         mcu::mac_address()
     }
 
-    fn into_parts(self) -> BoardParts<RadioParts, UsbParts, DisplayParts, Ws2812> {
+    fn into_parts(self) -> BoardParts<RadioParts, UsbParts, DisplayParts, LedDriver> {
         let p = self.p;
 
         mcu::start_timer(p.TIMG0);
@@ -77,18 +75,9 @@ impl LoRaBoard for Board {
         let i2c = mcu::init_i2c(p.I2C0, p.GPIO17, p.GPIO18);
         let display = Some(DisplayParts { i2c });
 
-        // WS2812B RGB LED on GPIO38 via RMT channel 0 (blocking, ~31µs per update)
-        let rmt = Rmt::new(p.RMT, Rate::from_mhz(80)).expect("RMT init");
-        let led_channel = rmt
-            .channel0
-            .configure_tx(
-                p.GPIO38,
-                TxChannelConfig::default()
-                    .with_clk_divider(1)
-                    .with_idle_output(true),
-            )
-            .expect("RMT TX channel init");
-        let led = Some(Ws2812::new(led_channel));
+        // Orange LED on GPIO35
+        let led_pin = Output::new(p.GPIO35, Level::Low, OutputConfig::default());
+        let led = Some(SimpleLed::new(led_pin));
 
         BoardParts {
             radio,