Add four Steins;Gate pages; shuffle the page rotation hourly

Divergence meter (Nixie tubes, world lines and clock), a D-mail sent
through the Phone Microwave using the panel's Message text, the Future
Gadget Lab inventory with live sensors, and a world line chart of today's
solar power. Original pixel art in tools/steins_sprites.py; the sprite
tool is shared between themes and Sprite, sprite(), polar() and arc()
move to el512_pages.h. HomeData gains the message and a 24 h solar
history in 15-minute slots.

The rotation now walks all pages in a random order that is reshuffled
every hour (Still Alive stays out, Now playing is skipped when idle).

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

components/el512/steins.h

@@ -0,0 +1,36 @@
+// Steins;Gate-themed animated pages for the ESPHome display: a Nixie-tube
+// divergence meter, a D-mail sent from a flip phone through the Phone
+// Microwave, the Future Gadget Lab inventory with live sensors, and a world
+// line chart of today's solar power. Fan art: the pixel art
+// (steins_sprites.h, from tools/steins_sprites.py) and all texts are original.
+//
+// Each function draws a whole page. Call it from a page lambda and list that
+// page under animated_pages; the animation clock is the display's page_age_ms().
+#pragma once
+
+#include "el512_pages.h"
+#include "esphome/components/display/display.h"
+#include "esphome/core/time.h"
+
+namespace esphome::el512 {
+
+class EL512Display;
+
+namespace steins {
+
+struct Fonts {
+  display::BaseFont *nixie{nullptr};  // Nixie tube digits (Nixie One)
+  display::BaseFont *title{nullptr};  // typewriter headers (Special Elite)
+  display::BaseFont *mono{nullptr};   // small monospace (Share Tech Mono 14)
+  display::BaseFont *code{nullptr};   // larger monospace (Share Tech Mono 22)
+  display::BaseFont *pixel{nullptr};  // phone LCD (Press Start 2P 8)
+  display::BaseFont *jp{nullptr};     // a few Japanese words (Noto Sans JP)
+};
+
+void divergence_meter(EL512Display &it, const Fonts &f, ESPTime now);
+void d_mail(EL512Display &it, const Fonts &f, const HomeData &d);
+void gadget_lab(EL512Display &it, const Fonts &f, const HomeData &d);
+void world_lines(EL512Display &it, const Fonts &f, const HomeData &d, ESPTime now);
+
+}  // namespace steins
+}  // namespace esphome::el512