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>

README.md

@@ -95,7 +95,7 @@ view of the display: it shows what the dots show right now, updated every 1.5 s.
 | Tab | What you can do |
 |-----|-----------------|
 | **Show** | Choose what the display shows during the day: a dynamic page (e.g. the built-in Clock: Pikachu with the time) or any bitmap. The schedule still decides when the display is on. |
-| **Pages** | Dynamic pages: a background bitmap per time of day (e.g. Pikachu from 00:00, yawning Pikachu from 17:00) with up to 8 elements on top: clock (`08:05` / `8:05`), date (7 formats, Dutch or English), Home Assistant value (entity or attribute, text before and after, decimals) and text. Each element has a position (drag it on the preview), alignment, font and overlay (on top, box that clears the dots behind it, inverted). The preview is drawn by the ESP32, so it is exactly what the display shows. Built-in pages can be copied, not changed. Fonts: Small (3x5), Normal (5x7), Large (5x7 doubled), Full height (19 dot digits), and your own: upload a TTF/OTF, choose the height in dots, the browser converts it. |
+| **Pages** | Dynamic pages: a background bitmap per time of day (e.g. Pikachu from 00:00, yawning Pikachu from 17:00) with up to 8 elements on top: clock (`08:05`, `8:05`, optionally with seconds), date (7 formats, Dutch or English), Home Assistant value (entity or attribute, text before and after, multiplier, decimals), text, countdown to a date and time (smart `12 dagen` / `5 uur` / `34 min` / `0:45`, days, `12d 04:05`, with seconds; a text when it has passed), stopwatch (start, stop and reset in the Show tab, the editor and Home Assistant) and image (a bitmap at a position, fixed or chosen by a Home Assistant state, e.g. `weather ` + `cloudy`). Texts can scroll in a window at a chosen speed, and can contain the degree sign. Each element has a position (drag it on the preview), alignment, font and overlay (on top, box that clears the dots behind it, inverted). The preview is drawn by the ESP32, so it is exactly what the display shows. Built-in pages can be copied, not changed. Fonts: Small (3x5), Normal (5x7), Large (5x7 doubled), Full height (19 dot digits), and your own: upload a TTF/OTF, choose the height in dots, the browser converts it. |
 | **Bitmaps** | All bitmaps with a preview: show one as the page, send it live, open it in the editor, delete it. The built-in ones (Nintendo, Pikachu, Pikachu yawning) can't be deleted, nor can a bitmap that a page uses as background. |
 | **Draw / Live** | Draw on an 84 x 19 canvas (click or drag), or load an image: it is converted in the browser (threshold, invert, dithering, fit / fill / stretch). "Show on display now" sends it to the display right away (*live mode*); with "live while drawing" every change appears on the dots. Save it as a bitmap with a name. |
 | **Settings** | Schedule on/off, when the display is on, the late-evening quarter-hour mode, when it switches off; the "No WiFi" screen; the flip time, the pause after each pulse, pulses per dot and the refresh effect (instant, sparkle, wipe, rain, from the middle out, diagonal, spiral, flip all then reveal, push, random; optionally only for small changes like the clock's minutes); test patterns; the status LED. |
@@ -111,6 +111,8 @@ a thousand bitmaps, 50 pages, 20 fonts). Pages and bitmaps share their names. Th
 the new flash layout from the [one-time installation](#one-time-installation-usb);
 before that, only the built-in ones are available.
 
+**Moving pages** (scrolling text, seconds, a running stopwatch) send a frame whenever the content moves, without the refresh effect (`D1`, needs the Nano firmware from version 2.5.0), and not faster than the Nano can flip the dots: with 3 pulses and a 300 us gap a 1-dot scroll step of a line of text takes about 0.1-0.2 s.
+
 **Home Assistant values** on the shown page are read every minute (one entity per loop,
 at most about 3 s). An unknown or unreachable value shows `--`. The display only changes
 when the shown text changes, so round values with the decimals setting.
@@ -308,6 +310,8 @@ The ESP32 talks to the Nano on **UART2** (`Serial2`, 115200 baud). The ESP32's o
    - `FlipDot Display Off image` dropdown: what is left on the dots when the display
      switches off (at night or with the Power switch): blank or one of the bitmaps.
    - `FlipDot Display IP` sensor: the ESP32's IP address.
+   - `FlipDot Display Stopwatch` switch and `FlipDot Display Stopwatch reset` button: the
+     stopwatch of the dynamic pages.
 4. **Nano.** The Nano reads commands from the serial line and updates its frame buffer.
    On `D` it flips only the dots that changed. Every 2 minutes it redraws the whole screen
    to fix dots that did not flip.