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/chrono/tests/win_bindings.rs

@@ -0,0 +1,39 @@
+use std::fs;
+use windows_bindgen::bindgen;
+
+#[test]
+fn gen_bindings() {
+    let existing = fs::read_to_string(BINDINGS).unwrap();
+
+    bindgen([
+        "--out",
+        BINDINGS,
+        "--flat",
+        "--no-comment",
+        "--no-deps",
+        "--sys",
+        "--filter",
+        "GetTimeZoneInformationForYear",
+        "SystemTimeToFileTime",
+        "SystemTimeToTzSpecificLocalTime",
+        "TzSpecificLocalTimeToSystemTime",
+    ])
+    .unwrap();
+
+    // Check the output is the same as before.
+    // Depending on the git configuration the file may have been checked out with `\r\n` newlines or
+    // with `\n`. Compare line-by-line to ignore this difference.
+    let mut new = fs::read_to_string(BINDINGS).unwrap();
+    if existing.contains("\r\n") && !new.contains("\r\n") {
+        new = new.replace("\n", "\r\n");
+    } else if !existing.contains("\r\n") && new.contains("\r\n") {
+        new = new.replace("\r\n", "\n");
+    }
+
+    similar_asserts::assert_eq!(existing, new);
+    if !new.lines().eq(existing.lines()) {
+        panic!("generated file `{BINDINGS}` is changed.");
+    }
+}
+
+const BINDINGS: &str = "src/offset/local/win_bindings.rs";