Add flight route lookup, helicopter marker, and QR code for WebUI

Detail panel now shows origin/destination via adsbdb.com callsign
lookup. Rotorcraft (ADS-B category A7) get a distinct rotor-cross
marker instead of a heading arrowhead, same rationale as the existing
ground-vehicle marker. WebUI info screen gets a QR button (when WiFi
is connected) that renders the local WebUI URL as a scannable code.

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

src/i18n_de.h

@@ -238,6 +238,8 @@ static const char* const I18N_DE[] = {
     "Lösche alle Daten...",
     "Zurücksetzen fehlgeschlagen.",
     "Tippen zum Überspringen",
+    "Route: ",
+    "Mit dem Handy scannen:",
 };
 
 static_assert(sizeof(I18N_DE) / sizeof(I18N_DE[0]) == (size_t)StringId::COUNT,