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_en.h

@@ -118,6 +118,7 @@ static const char* const I18N_EN[] = {
     "Tap again to confirm!",
     "Logbook data reset.",
     "Uptime: ",
+    "Highest flight today: ",
     "History (last 7 days)",
     "No logbook entries yet.",
     "How the history chart works",