Game of Life page element and built-in page

A new page element runs Conway's Game of Life in an area (the whole display
by default), one per page. Start: random dots, one pattern, or the icons
whose names start with a text in turn or in random order. Edges: wrap
around, dead, or a hidden margin where gliders fly out of view (leftovers
that stay put in the margin are cleared, so a glider gun runs cleanly).
It restarts when the board is still or repeats within 16 generations
and/or after a number of generations, after a hold time (an empty board
at once).

logic/life holds the board and timing (tested), display/life_player runs
the board of the shown page, ticked before each frame; frames are paced
like scrolling text. The element reuses existing fields, so the page
format stays the same. The Icons tab has a library of 17 LifeWiki
patterns (checked with a simulation), and the built-in page "Game of
Life" shuffles through the life_ icons. About 12 KB flash, 8 KB RAM.

Version 2.17.0, tested on the display over OTA.

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

docs/how-it-works.md

@@ -13,6 +13,14 @@
    - **08:00–23:30:** the page: the chosen page (by default the built-in Clock page,
      Pikachu with a thought bubble showing `HH:MM`, yawning from 17:00), or what the
      [schedule and rules](web-ui.md#schedule) pick.
+   - **Game of Life** (a page element): the ESP32 runs the board (`logic/life`) and sends a
+     frame per generation with only the changed dots. Like scrolling text, the next frame
+     waits until the Nano has received and flipped the last one, so a busy board runs
+     slower than the chosen speed. Only the shown page runs; it pauses while the display is
+     off. Still or repeating boards are found by comparing a hash of the board with the
+     last 16 generations. With the hidden margin, gliders that leave the area are cleared
+     at the outer edge, and leftovers that stay put in the margin are cleared after 12
+     generations, so a glider gun keeps running cleanly.
    - **Slow mode** (a switch in Home Assistant and the web UI, for less noise): the display
      only changes every 1, 2, 5, 10, 15, 20, 30 or 60 minutes, on the clock (15 minutes =
      :00, :15, :30 and :45). 30 seconds after each update the relay turns the display off;