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/usb0/hfnum.rs

@@ -0,0 +1,38 @@
+#[doc = "Register `HFNUM` reader"]
+pub type R = crate::R<HFNUM_SPEC>;
+#[doc = "Field `FRNUM` reader - "]
+pub type FRNUM_R = crate::FieldReader<u16>;
+#[doc = "Field `FRREM` reader - "]
+pub type FRREM_R = crate::FieldReader<u16>;
+impl R {
+    #[doc = "Bits 0:13"]
+    #[inline(always)]
+    pub fn frnum(&self) -> FRNUM_R {
+        FRNUM_R::new((self.bits & 0x3fff) as u16)
+    }
+    #[doc = "Bits 16:31"]
+    #[inline(always)]
+    pub fn frrem(&self) -> FRREM_R {
+        FRREM_R::new(((self.bits >> 16) & 0xffff) as u16)
+    }
+}
+#[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("HFNUM")
+            .field("frnum", &self.frnum())
+            .field("frrem", &self.frrem())
+            .finish()
+    }
+}
+#[doc = "\n\nYou can [`read`](crate::Reg::read) this register and get [`hfnum::R`](R). See [API](https://docs.rs/svd2rust/#read--modify--write-api)."]
+pub struct HFNUM_SPEC;
+impl crate::RegisterSpec for HFNUM_SPEC {
+    type Ux = u32;
+}
+#[doc = "`read()` method returns [`hfnum::R`](R) reader structure"]
+impl crate::Readable for HFNUM_SPEC {}
+#[doc = "`reset()` method sets HFNUM to value 0x3fff"]
+impl crate::Resettable for HFNUM_SPEC {
+    const RESET_VALUE: u32 = 0x3fff;
+}