v2.6.0: Show highest-altitude flight of the day on Statistics screen

Adds FlightLogbook::todayMaxAltitude(), which scans today's logbook
CSV for the entry with the greatest altitude at first sighting, and
displays it as "Highest flight today: <callsign> (<alt> ft)" on the
Statistics screen (Menu -> Flight Options -> Statistics).

Also documents the CYD-flightradar.bin rename step (for GitHub
release uploads) in the CLAUDE.md release workflow.

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

src/i18n_es.h

@@ -117,6 +117,7 @@ static const char* const I18N_ES[] = {
     "¡Toque de nuevo para confirmar!",
     "Registro reiniciado.",
     "Tiempo activo: ",
+    "Vuelo más alto hoy: ",
     "Historial (últimos 7 días)",
     "Aún no hay registros.",
     "Cómo funciona el historial",