Add WebUI live radar; mutex-protect AirlineFilter/AircraftWatchlist

The WebUI home page now shows a live radar canvas above the flight
logbook, polling a new /radar.json endpoint every 3 seconds. It
mirrors the device display: distance rings, aircraft colored by
altitude, ground vehicles as squares, rotorcraft as diamonds, and
emergency/watchlist/heavy-category rings in that priority. Applies
the same range, hide-ground-vehicles, and airline filters as the
device radar.

AirlineFilter and AircraftWatchlist gain proper mutex protection
around their in-memory arrays (previously only guarded around SD
file I/O) since the new /lists WebUI pages reach them from Core 0
(NetTask) in addition to their existing Core 1 (menu screen)
callers.

Note: the "notable aircraft" military/government callsign-prefix
marker is not implemented - Config::NOTABLE_CALLSIGN_PREFIXES was
never defined anywhere in this project, on the device display or
here. The "notable" ring currently fires on heavy-category aircraft
only.

Also documents the OTA-testing exception to the auto-flash rule in
CLAUDE.md (build-only during Push & Release, so the test device stays
on the previous version for OTA testing).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/i18n_it.h

@@ -198,7 +198,7 @@ static const char* const I18N_IT[] = {
 
     "Registro / WebUI",
     "Registro / WebUI",
-    "Questa pagina web permette di visualizzare, scaricare ed eliminare singolarmente il registro di volo direttamente dal browser. Connesso alla stessa rete WiFi, apri un browser e vai a:",
+    "Questa pagina web mostra in alto un radar dal vivo con tutti gli aerei attualmente visibili e, sotto, permette di visualizzare, scaricare ed eliminare singolarmente il registro di volo direttamente dal browser. Connesso alla stessa rete WiFi, apri un browser e vai a:",
     "Nessuna connessione WiFi - la pagina è raggiungibile solo mentre è attiva una connessione di rete.",
 
     "Meteo",