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/esp32s3/src/sens/sar_touch_status0.rs

@@ -0,0 +1,30 @@
+#[doc = "Register `SAR_TOUCH_STATUS0` reader"]
+pub type R = crate::R<SAR_TOUCH_STATUS0_SPEC>;
+#[doc = "Field `SAR_TOUCH_SCAN_CURR` reader - current sample channel"]
+pub type SAR_TOUCH_SCAN_CURR_R = crate::FieldReader;
+impl R {
+    #[doc = "Bits 22:25 - current sample channel"]
+    #[inline(always)]
+    pub fn sar_touch_scan_curr(&self) -> SAR_TOUCH_SCAN_CURR_R {
+        SAR_TOUCH_SCAN_CURR_R::new(((self.bits >> 22) & 0x0f) as u8)
+    }
+}
+#[cfg(feature = "impl-register-debug")]
+impl core::fmt::Debug for R {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+        f.debug_struct("SAR_TOUCH_STATUS0")
+            .field("sar_touch_scan_curr", &self.sar_touch_scan_curr())
+            .finish()
+    }
+}
+#[doc = "get touch scan status\n\nYou can [`read`](crate::Reg::read) this register and get [`sar_touch_status0::R`](R). See [API](https://docs.rs/svd2rust/#read--modify--write-api)."]
+pub struct SAR_TOUCH_STATUS0_SPEC;
+impl crate::RegisterSpec for SAR_TOUCH_STATUS0_SPEC {
+    type Ux = u32;
+}
+#[doc = "`read()` method returns [`sar_touch_status0::R`](R) reader structure"]
+impl crate::Readable for SAR_TOUCH_STATUS0_SPEC {}
+#[doc = "`reset()` method sets SAR_TOUCH_STATUS0 to value 0"]
+impl crate::Resettable for SAR_TOUCH_STATUS0_SPEC {
+    const RESET_VALUE: u32 = 0;
+}