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/konosuba.cpp

@@ -21,45 +21,10 @@ namespace {
 using namespace fx;
 
 constexpr int W = 512, H = 256;
-constexpr float DEG = 3.14159265f / 180.0f;
 const uint8_t BAYER[4][4] = {{0, 8, 2, 10}, {12, 4, 14, 6}, {3, 11, 1, 9}, {15, 7, 13, 5}};
 
 // --- Drawing helpers -----------------------------------------------------------
 
-// Draw a sprite (optionally only its first `rows` rows), scaled up in blocks.
-void sprite(Display &it, const Sprite &s, int x, int y, int scale = 1, int rows = -1, Color color = COLOR_ON) {
-  const int h = rows < 0 ? s.h : std::min<int>(rows, s.h);
-  for (int r = 0; r < h; r++) {
-    for (int c = 0; c < s.w; c++) {
-      if (s.rows[r][c] != '#')
-        continue;
-      if (scale == 1)
-        it.draw_pixel_at(x + c, y + r, color);
-      else
-        it.filled_rectangle(x + c * scale, y + r * scale, scale, scale, color);
-    }
-  }
-}
-
-// Point on a circle; angle in degrees, 0 = up, clockwise.
-void polar(int cx, int cy, float r, float a, int *x, int *y) {
-  *x = cx + (int) std::lround(r * std::sin(a * DEG));
-  *y = cy - (int) std::lround(r * std::cos(a * DEG));
-}
-
-void arc(Display &it, int cx, int cy, float r, float a0, float a1) {
-  const int steps = std::max(2, (int) (std::fabs(a1 - a0) / 5));
-  int px, py;
-  polar(cx, cy, r, a0, &px, &py);
-  for (int i = 1; i <= steps; i++) {
-    int nx, ny;
-    polar(cx, cy, r, a0 + (a1 - a0) * i / steps, &nx, &ny);
-    it.line(px, py, nx, ny);
-    px = nx;
-    py = ny;
-  }
-}
-
 // Four-point twinkle.
 void sparkle(Display &it, int x, int y, int r) {
   it.horizontal_line(x - r, y, 2 * r + 1);