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);
+    }
+}

vendor/semver/tests/regression.rs

@@ -0,0 +1,25 @@
+extern crate semver;
+extern crate crates_index;
+extern crate tempdir;
+
+// This test checks to see if every existing crate parses successfully. Important to not break the
+// Rust universe!
+
+#[cfg(feature = "ci")]
+#[test]
+fn test_regressions() {
+    use tempdir::TempDir;
+    use crates_index::Index;
+    use semver::Version;
+
+    let dir = TempDir::new("semver").unwrap();
+    let index = Index::new(dir.into_path());
+    index.clone().unwrap();
+
+    for krate in index.crates() {
+        for version in krate.versions() {
+            let v = version.version();
+            assert!(Version::parse(v).is_ok(), "failed: {} ({})", version.name(), v);
+        }
+    }
+}

vendor/semver/tests/serde.rs

@@ -0,0 +1,90 @@
+#![cfg(feature = "serde")]
+
+#[macro_use]
+extern crate serde_derive;
+
+extern crate semver;
+extern crate serde_json;
+
+use semver::{Identifier, Version, VersionReq};
+
+#[derive(Serialize, Deserialize, PartialEq, Debug)]
+struct Identified {
+    name: String,
+    identifier: Identifier,
+}
+
+#[derive(Serialize, Deserialize, PartialEq, Debug)]
+struct Versioned {
+    name: String,
+    vers: Version,
+}
+
+#[test]
+fn serialize_identifier() {
+    let id = Identified {
+        name: "serde".to_owned(),
+        identifier: Identifier::Numeric(100),
+    };
+    let j = serde_json::to_string(&id).unwrap();
+    assert_eq!(j, r#"{"name":"serde","identifier":100}"#);
+
+    let id = Identified {
+        name: "serde".to_owned(),
+        identifier: Identifier::AlphaNumeric("b100".to_owned()),
+    };
+    let j = serde_json::to_string(&id).unwrap();
+    assert_eq!(j, r#"{"name":"serde","identifier":"b100"}"#);
+}
+
+#[test]
+fn deserialize_identifier() {
+    let j = r#"{"name":"serde","identifier":100}"#;
+    let id = serde_json::from_str::<Identified>(j).unwrap();
+    let expected = Identified {
+        name: "serde".to_owned(),
+        identifier: Identifier::Numeric(100),
+    };
+    assert_eq!(id, expected);
+
+    let j = r#"{"name":"serde","identifier":"b100"}"#;
+    let id = serde_json::from_str::<Identified>(j).unwrap();
+    let expected = Identified {
+        name: "serde".to_owned(),
+        identifier: Identifier::AlphaNumeric("b100".to_owned()),
+    };
+    assert_eq!(id, expected);
+}
+
+#[test]
+fn serialize_version() {
+    let v = Versioned {
+        name: "serde".to_owned(),
+        vers: Version::parse("1.0.0").unwrap(),
+    };
+    let j = serde_json::to_string(&v).unwrap();
+    assert_eq!(j, r#"{"name":"serde","vers":"1.0.0"}"#);
+}
+
+#[test]
+fn deserialize_version() {
+    let j = r#"{"name":"serde","vers":"1.0.0"}"#;
+    let v = serde_json::from_str::<Versioned>(j).unwrap();
+    let expected = Versioned {
+        name: "serde".to_owned(),
+        vers: Version::parse("1.0.0").unwrap(),
+    };
+    assert_eq!(v, expected);
+}
+
+#[test]
+fn serialize_versionreq() {
+    let v = VersionReq::exact(&Version::parse("1.0.0").unwrap());
+
+    assert_eq!(serde_json::to_string(&v).unwrap(), r#""= 1.0.0""#);
+}
+
+#[test]
+fn deserialize_versionreq() {
+    assert_eq!("1.0.0".parse::<VersionReq>().unwrap(), serde_json::from_str(r#""1.0.0""#).unwrap());
+}