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/thiserror/tests/ui/lifetime.rs

@@ -0,0 +1,24 @@
+use core::fmt::Debug;
+use thiserror::Error;
+
+#[derive(Error, Debug)]
+#[error("error")]
+struct Error<'a>(#[from] Inner<'a>);
+
+#[derive(Error, Debug)]
+#[error("{0}")]
+struct Inner<'a>(&'a str);
+
+#[derive(Error, Debug)]
+enum Enum<'a> {
+    #[error("error")]
+    Foo(#[from] Generic<&'a str>),
+}
+
+#[derive(Error, Debug)]
+#[error("{0:?}")]
+struct Generic<T: Debug>(T);
+
+fn main() -> Result<(), Error<'static>> {
+    Err(Error(Inner("some text")))
+}