v2.4.0: Night dimming, aircraft watchlist, and nearest-airport lookup

src/aircraft_watchlist.h

@@ -0,0 +1,16 @@
+#pragma once
+#include <Arduino.h>
+
+namespace AircraftWatchlist {
+    constexpr uint8_t MAX_WATCHED = 5;
+
+    void init();
+
+    uint8_t count();
+    String callsignAt(uint8_t index);
+
+    bool addWatched(const char* callsign);
+    void removeWatched(uint8_t index);
+
+    bool isWatched(const char* callsign);
+}