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/embedded-graphics/benches/contains.rs

@@ -0,0 +1,28 @@
+use criterion::*;
+use embedded_graphics::{prelude::*, primitives::*};
+
+fn triangle_contains_inside(c: &mut Criterion) {
+    c.bench_function("triangle contains point (inside)", |b| {
+        let object = Triangle::new(Point::new(5, 10), Point::new(15, 20), Point::new(5, 20));
+        let midpoint = object.bounding_box().center();
+
+        b.iter(|| object.contains(midpoint))
+    });
+}
+
+// Point outside triangle but still within bounding box. If point is outside bounding box, this
+// benchmark doesn't exercise the expensive point-in-triangle code.
+fn triangle_contains_outside(c: &mut Criterion) {
+    c.bench_function("triangle contains point (outside)", |b| {
+        let object = Triangle::new(Point::new(5, 10), Point::new(55, 20), Point::new(30, 40));
+
+        b.iter(|| object.contains(Point::new(50, 13)))
+    });
+}
+
+criterion_group!(
+    contains,
+    triangle_contains_inside,
+    triangle_contains_outside
+);
+criterion_main!(contains);