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/nano/README.md

@@ -78,7 +78,7 @@ skipped and the next line starts clean. Coordinates are 2-digit **hex**. Color i
 | `s` | `sXXYYc` | Set pixel in the buffer |
 | `S` | `SXXYYc` | Set pixel and flip it right away (direct mode) |
 | `F` | `Fc` | Fill the whole buffer |
-| `D` | `D` | Push the buffer to the display (changed dots only) |
+| `D` | `D` or `D1` | Push the buffer to the display (changed dots only). `D1`: a frame of moving content (scrolling text, seconds), shown without the refresh effect; the periodic full redraw then waits until the serial line is idle. |
 | `P` | `PXXYYcsTEXT` | Print text at (XX,YY), color `c`, size `s`. A literal `\n` (backslash, n) in TEXT starts a new line. The whole line can be at most 64 characters. |
 | `B` | `BXXYYWWHHcHEX...` | Draw a bitmap. WW must be a multiple of 4. Pixel data is one hex digit per 4 pixels, row by row. The data is drawn while it arrives, so it is not limited to 64 characters. |
 | `R` | `R` | Print the buffer as ASCII art on the serial port |