Add scrolling, countdown, stopwatch, images, seconds, multiplier and degree sign

- Text elements can scroll in a window at a set speed; clock, countdown and
  stopwatch can show seconds. Moving pages are sent as instant frames (new
  Nano command D1) and paced by the estimated flip time.
- Countdown to a date and time (smart, days, days + time, with seconds),
  stopwatch (web UI, HA switch and reset button), image element (fixed or
  by Home Assistant state), multiplier for HA values, degree sign (char 127)
  in all fonts and the font converter.
- Page format version 2; version 1 pages are converted.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/esp32/net/home_assistant.h

@@ -12,6 +12,8 @@
 //   FlipDot Display IP        sensor: the IP address
 //   FlipDot Display Firmware  sensor: version and health, e.g. "2.1.0, ok, 0 crashes, ..."
 //   FlipDot Display Recovery  button: restart into the recovery app (for 10 minutes)
+//   FlipDot Display Stopwatch switch: the stopwatch of the dynamic pages runs
+//   FlipDot Display Stopwatch reset  button: back to 0
 //
 // The broker comes from the settings (web UI); an empty host means BROKER_ADDR, MQTT_USER
 // and MQTT_PASSWORD from secrets.h. Changes need a restart.