Schedule pages and rotation rules can be skipped in slow mode

Each page in a schedule block, and each rule that adds its page to the
rotation, has a "skip in slow mode" checkbox. While slow mode is on those
pages are left out of the rotation; when none of the block's pages are
left, the chosen page is shown. The rotation keeps its own timers.

Schedule format version 5; version 4 is converted when read and stored
again in version 5 on the next save.

Version 2.18.0.

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

docs/home-assistant.md

@@ -26,7 +26,8 @@ The ESP32 connects to Home Assistant in two ways:
 - `FlipDot Display Slow mode` switch and `FlipDot Display Slow mode interval` dropdown
   (`1 minute` ... `60 minutes`): the display only changes at those times, on the clock, and
   is switched off in between (less noise, e.g. in the evening with an automation). Rules
-  with "show at once in slow mode" still show their page right away.
+  with "show at once in slow mode" still show their page right away; pages with "skip in
+  slow mode" are left out of the rotation.
 - `FlipDot Display Firmware` sensor: version and health, e.g. `2.7.2, ok, 0 crashes, recovery ok`.
 - `FlipDot Display Recovery` button: restarts into the [recovery app](recovery.md) for 10
   minutes.

docs/how-it-works.md

@@ -26,6 +26,8 @@
      :00, :15, :30 and :45). 30 seconds after each update the relay turns the display off;
      the dots keep the image. Page changes wait for the next update too, except for rules
      with "show at once in slow mode": while their page is shown, the display works normally.
+     Schedule pages and rotation rules with "skip in slow mode" are left out of the rotation
+     (none left in the block: the chosen page).
    - **23:31–08:00:** the screen is cleared (or shows the off image chosen in the web UI)
      and power is cut after 30 seconds.
 3. **Home Assistant**: switches, dropdowns and sensors over MQTT, see

docs/web-ui.md

@@ -70,7 +70,11 @@ interval (2-600 s) and can be limited to some of the blocks. The first rule that
 page wins. A rule can leave a page chosen by hand alone (untick "also over a page chosen by
 hand"): it then waits until that pick ends (the next block or "Back to schedule"). A rule
 with "show at once in slow mode" ticked brings its page right away in
-[slow mode](#settings), and the display works normally while that page is shown. The display schedule ([Settings](#settings)) still decides when the display is on.
+[slow mode](#settings), and the display works normally while that page is shown.
+
+Pages in a block, and rules that add their page to the rotation, can be left out while slow
+mode is on ("skip in slow mode"). When that leaves none of a block's pages, the chosen page
+is shown instead. The display schedule ([Settings](#settings)) still decides when the display is on.
 
 ![Schedule](../Pictures/web-ui/schedule.png)