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/nrf52805-pac/src/qdec/acc.rs

@@ -0,0 +1,40 @@
+#[doc = "Register `ACC` reader"]
+pub struct R(crate::R<ACC_SPEC>);
+impl core::ops::Deref for R {
+    type Target = crate::R<ACC_SPEC>;
+    #[inline(always)]
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+impl From<crate::R<ACC_SPEC>> for R {
+    #[inline(always)]
+    fn from(reader: crate::R<ACC_SPEC>) -> Self {
+        R(reader)
+    }
+}
+#[doc = "Field `ACC` reader - Register accumulating all valid samples (not double transition) read from the SAMPLE register."]
+pub type ACC_R = crate::FieldReader<u32, u32>;
+impl R {
+    #[doc = "Bits 0:31 - Register accumulating all valid samples (not double transition) read from the SAMPLE register."]
+    #[inline(always)]
+    pub fn acc(&self) -> ACC_R {
+        ACC_R::new(self.bits)
+    }
+}
+#[doc = "Register accumulating the valid transitions\n\nThis register you can [`read`](crate::generic::Reg::read). See [API](https://docs.rs/svd2rust/#read--modify--write-api).\n\nFor information about available fields see [acc](index.html) module"]
+pub struct ACC_SPEC;
+impl crate::RegisterSpec for ACC_SPEC {
+    type Ux = u32;
+}
+#[doc = "`read()` method returns [acc::R](R) reader structure"]
+impl crate::Readable for ACC_SPEC {
+    type Reader = R;
+}
+#[doc = "`reset()` method sets ACC to value 0"]
+impl crate::Resettable for ACC_SPEC {
+    #[inline(always)]
+    fn reset_value() -> Self::Ux {
+        0
+    }
+}