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/nrf5340-app-pac/src/cache_s/erase.rs

@@ -0,0 +1,71 @@
+#[doc = "Register `ERASE` writer"]
+pub struct W(crate::W<ERASE_SPEC>);
+impl core::ops::Deref for W {
+    type Target = crate::W<ERASE_SPEC>;
+    #[inline(always)]
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+impl core::ops::DerefMut for W {
+    #[inline(always)]
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        &mut self.0
+    }
+}
+impl From<crate::W<ERASE_SPEC>> for W {
+    #[inline(always)]
+    fn from(writer: crate::W<ERASE_SPEC>) -> Self {
+        W(writer)
+    }
+}
+#[doc = "Erase the cache\n\nValue on reset: 0"]
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub enum ERASE_AW {
+    #[doc = "1: Erase cache"]
+    ERASE = 1,
+}
+impl From<ERASE_AW> for bool {
+    #[inline(always)]
+    fn from(variant: ERASE_AW) -> Self {
+        variant as u8 != 0
+    }
+}
+#[doc = "Field `ERASE` writer - Erase the cache"]
+pub type ERASE_W<'a, const O: u8> = crate::BitWriter<'a, u32, ERASE_SPEC, ERASE_AW, O>;
+impl<'a, const O: u8> ERASE_W<'a, O> {
+    #[doc = "Erase cache"]
+    #[inline(always)]
+    pub fn erase(self) -> &'a mut W {
+        self.variant(ERASE_AW::ERASE)
+    }
+}
+impl W {
+    #[doc = "Bit 0 - Erase the cache"]
+    #[inline(always)]
+    pub fn erase(&mut self) -> ERASE_W<0> {
+        ERASE_W::new(self)
+    }
+    #[doc = "Writes raw bits to the register."]
+    #[inline(always)]
+    pub unsafe fn bits(&mut self, bits: u32) -> &mut Self {
+        self.0.bits(bits);
+        self
+    }
+}
+#[doc = "Erase the cache.\n\nThis register you can [`write_with_zero`](crate::generic::Reg::write_with_zero), [`reset`](crate::generic::Reg::reset), [`write`](crate::generic::Reg::write). See [API](https://docs.rs/svd2rust/#read--modify--write-api).\n\nFor information about available fields see [erase](index.html) module"]
+pub struct ERASE_SPEC;
+impl crate::RegisterSpec for ERASE_SPEC {
+    type Ux = u32;
+}
+#[doc = "`write(|w| ..)` method takes [erase::W](W) writer structure"]
+impl crate::Writable for ERASE_SPEC {
+    type Writer = W;
+}
+#[doc = "`reset()` method sets ERASE to value 0"]
+impl crate::Resettable for ERASE_SPEC {
+    #[inline(always)]
+    fn reset_value() -> Self::Ux {
+        0
+    }
+}