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/semver/tests/deprecation.rs

@@ -0,0 +1,22 @@
+extern crate semver;
+
+#[test]
+fn test_regressions() {
+    use semver::VersionReq;
+    use semver::ReqParseError;
+
+    let versions = vec![
+        (".*", VersionReq::any()),
+        ("0.1.0.", VersionReq::parse("0.1.0").unwrap()),
+        ("0.3.1.3", VersionReq::parse("0.3.13").unwrap()),
+        ("0.2*", VersionReq::parse("0.2.*").unwrap()),
+        ("*.0", VersionReq::any()),
+    ];
+
+    for (version, requirement) in versions.into_iter() {
+        let parsed = VersionReq::parse(version);
+        let error = parsed.err().unwrap();
+
+        assert_eq!(ReqParseError::DeprecatedVersionRequirement(requirement), error);
+    }
+}