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/rng/data.rs

@@ -0,0 +1,19 @@
+#[doc = "Register `DATA` reader"]
+pub type R = crate::R<DATA_SPEC>;
+#[cfg(feature = "impl-register-debug")]
+impl core::fmt::Debug for R {
+    fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+        write!(f, "{}", self.bits())
+    }
+}
+#[doc = "Random number data\n\nYou can [`read`](crate::Reg::read) this register and get [`data::R`](R). See [API](https://docs.rs/svd2rust/#read--modify--write-api)."]
+pub struct DATA_SPEC;
+impl crate::RegisterSpec for DATA_SPEC {
+    type Ux = u32;
+}
+#[doc = "`read()` method returns [`data::R`](R) reader structure"]
+impl crate::Readable for DATA_SPEC {}
+#[doc = "`reset()` method sets DATA to value 0"]
+impl crate::Resettable for DATA_SPEC {
+    const RESET_VALUE: u32 = 0;
+}