feat: add display UI with splash screen, dashboard, and RSSI sparkline

Implement full SSD1306 OLED display support:
- Splash screen on boot (1.5s) with project name, version, board
- Dashboard showing radio state, config, counters, RSSI/SNR
- RSSI history sparkline (64-sample ring buffer, 2px-wide bars)
- DisplayOn/DisplayOff host commands routed via dedicated channel
- Pure render functions against generic DrawTarget (no hardware coupling)
- Display on/off control bypasses radio task entirely

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/lora-phy/src/iv.rs

@@ -0,0 +1,173 @@
+use embedded_hal::digital::OutputPin;
+use embedded_hal_async::delay::DelayNs;
+use embedded_hal_async::digital::Wait;
+
+use crate::mod_params::RadioError;
+use crate::mod_params::RadioError::*;
+use crate::mod_traits::InterfaceVariant;
+
+/// Base for the InterfaceVariant implementation for the Sx127x combination
+pub struct GenericSx127xInterfaceVariant<CTRL, WAIT> {
+    reset: CTRL,
+    irq: WAIT,
+    rf_switch_rx: Option<CTRL>,
+    rf_switch_tx: Option<CTRL>,
+}
+
+impl<CTRL, WAIT> GenericSx127xInterfaceVariant<CTRL, WAIT>
+where
+    CTRL: OutputPin,
+    WAIT: Wait,
+{
+    /// Create an InterfaceVariant instance for an stm32l0/sx1276 combination
+    pub fn new(
+        reset: CTRL,
+        irq: WAIT,
+        rf_switch_rx: Option<CTRL>,
+        rf_switch_tx: Option<CTRL>,
+    ) -> Result<Self, RadioError> {
+        Ok(Self {
+            reset,
+            irq,
+            rf_switch_rx,
+            rf_switch_tx,
+        })
+    }
+}
+
+impl<CTRL, WAIT> InterfaceVariant for GenericSx127xInterfaceVariant<CTRL, WAIT>
+where
+    CTRL: OutputPin,
+    WAIT: Wait,
+{
+    async fn reset(&mut self, delay: &mut impl DelayNs) -> Result<(), RadioError> {
+        delay.delay_ms(10).await;
+        self.reset.set_low().map_err(|_| Reset)?;
+        delay.delay_ms(10).await;
+        self.reset.set_high().map_err(|_| Reset)?;
+        delay.delay_ms(10).await;
+        Ok(())
+    }
+    async fn wait_on_busy(&mut self) -> Result<(), RadioError> {
+        Ok(())
+    }
+    async fn await_irq(&mut self) -> Result<(), RadioError> {
+        self.irq.wait_for_high().await.map_err(|_| Irq)
+    }
+
+    async fn enable_rf_switch_rx(&mut self) -> Result<(), RadioError> {
+        match &mut self.rf_switch_tx {
+            Some(pin) => pin.set_low().map_err(|_| RfSwitchTx)?,
+            None => (),
+        };
+        match &mut self.rf_switch_rx {
+            Some(pin) => pin.set_high().map_err(|_| RfSwitchRx),
+            None => Ok(()),
+        }
+    }
+    async fn enable_rf_switch_tx(&mut self) -> Result<(), RadioError> {
+        match &mut self.rf_switch_rx {
+            Some(pin) => pin.set_low().map_err(|_| RfSwitchRx)?,
+            None => (),
+        };
+        match &mut self.rf_switch_tx {
+            Some(pin) => pin.set_high().map_err(|_| RfSwitchTx),
+            None => Ok(()),
+        }
+    }
+    async fn disable_rf_switch(&mut self) -> Result<(), RadioError> {
+        match &mut self.rf_switch_rx {
+            Some(pin) => pin.set_low().map_err(|_| RfSwitchRx)?,
+            None => (),
+        };
+        match &mut self.rf_switch_tx {
+            Some(pin) => pin.set_low().map_err(|_| RfSwitchTx),
+            None => Ok(()),
+        }
+    }
+}
+
+/// Base for the InterfaceVariant implementation for a generic Sx126x LoRa board
+pub struct GenericSx126xInterfaceVariant<CTRL, WAIT> {
+    reset: CTRL,
+    dio1: WAIT,
+    busy: WAIT,
+    rf_switch_rx: Option<CTRL>,
+    rf_switch_tx: Option<CTRL>,
+}
+
+impl<CTRL, WAIT> GenericSx126xInterfaceVariant<CTRL, WAIT>
+where
+    CTRL: OutputPin,
+    WAIT: Wait,
+{
+    /// Create an InterfaceVariant instance for an nrf52840/sx1262 combination
+    pub fn new(
+        reset: CTRL,
+        dio1: WAIT,
+        busy: WAIT,
+        rf_switch_rx: Option<CTRL>,
+        rf_switch_tx: Option<CTRL>,
+    ) -> Result<Self, RadioError> {
+        Ok(Self {
+            reset,
+            dio1,
+            busy,
+            rf_switch_rx,
+            rf_switch_tx,
+        })
+    }
+}
+
+impl<CTRL, WAIT> InterfaceVariant for GenericSx126xInterfaceVariant<CTRL, WAIT>
+where
+    CTRL: OutputPin,
+    WAIT: Wait,
+{
+    async fn reset(&mut self, delay: &mut impl DelayNs) -> Result<(), RadioError> {
+        delay.delay_ms(10).await;
+        self.reset.set_low().map_err(|_| Reset)?;
+        delay.delay_ms(20).await;
+        self.reset.set_high().map_err(|_| Reset)?;
+        delay.delay_ms(10).await;
+        Ok(())
+    }
+    async fn wait_on_busy(&mut self) -> Result<(), RadioError> {
+        self.busy.wait_for_low().await.map_err(|_| Busy)
+    }
+    async fn await_irq(&mut self) -> Result<(), RadioError> {
+        self.dio1.wait_for_high().await.map_err(|_| DIO1)?;
+        Ok(())
+    }
+
+    async fn enable_rf_switch_rx(&mut self) -> Result<(), RadioError> {
+        match &mut self.rf_switch_tx {
+            Some(pin) => pin.set_low().map_err(|_| RfSwitchTx)?,
+            None => (),
+        };
+        match &mut self.rf_switch_rx {
+            Some(pin) => pin.set_high().map_err(|_| RfSwitchRx),
+            None => Ok(()),
+        }
+    }
+    async fn enable_rf_switch_tx(&mut self) -> Result<(), RadioError> {
+        match &mut self.rf_switch_rx {
+            Some(pin) => pin.set_low().map_err(|_| RfSwitchRx)?,
+            None => (),
+        };
+        match &mut self.rf_switch_tx {
+            Some(pin) => pin.set_high().map_err(|_| RfSwitchTx),
+            None => Ok(()),
+        }
+    }
+    async fn disable_rf_switch(&mut self) -> Result<(), RadioError> {
+        match &mut self.rf_switch_rx {
+            Some(pin) => pin.set_low().map_err(|_| RfSwitchRx)?,
+            None => (),
+        };
+        match &mut self.rf_switch_tx {
+            Some(pin) => pin.set_low().map_err(|_| RfSwitchTx),
+            None => Ok(()),
+        }
+    }
+}