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/winnow/examples/c_expression/bench.rs

@@ -0,0 +1,16 @@
+mod parser;
+
+use criterion::black_box;
+use winnow::prelude::*;
+
+fn pratt(c: &mut criterion::Criterion) {
+    let i =
+        "a = 2*-2 / ( &**foo.a->p! -+1) + 3^1 / 4 == 1 * (2 - 7 + 567 *12 /2) + 3*(1+2*( 45 /2))";
+    parser::pratt_parser.parse(i).expect("should parse");
+    c.bench_function("pratt_parser", |b| {
+        b.iter(|| black_box(parser::pratt_parser.parse(i).unwrap()));
+    });
+}
+
+criterion::criterion_group!(benches, pratt);
+criterion::criterion_main!(benches);