Add four animated KonoSuba ESPHome pages

Megumin's daily explosion, the Adventurers' Guild quest board (agenda,
weather, solar), Megumin's adventurer card and a party battle against a
giant toad with a live-data battle log. Original 1-bit pixel art lives in
tools/konosuba_sprites.py, which generates konosuba_sprites.h and can
render a preview PNG.

Home data and drawing helpers shared by the themed pages move to
el512_pages.h; the display gains dither_mask() for a dissolve-in intro.

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

components/el512/el512_pages.h

@@ -0,0 +1,72 @@
+// Shared pieces for the themed ESPHome pages (cyberpunk.cpp, konosuba.cpp): the
+// Home Assistant values they show, and small drawing helpers.
+#pragma once
+
+#include <cctype>
+#include <cmath>
+#include <cstdarg>
+#include <cstdint>
+#include <cstdio>
+#include <string>
+
+#include "esphome/components/display/display.h"
+
+namespace esphome::el512 {
+
+struct Reading {
+  std::string name;
+  float value{NAN};
+};
+
+// Home Assistant values shown on the pages; NAN or "" when unknown. Filled
+// from YAML (see the cp_home global in el512-panel.yaml).
+struct HomeData {
+  std::string weather;     // condition, e.g. "partlycloudy"
+  float temp{NAN};         // °C
+  float humidity{NAN};     // %
+  float wind{NAN};         // km/h
+  float solar{NAN};        // W
+  float solar_today{NAN};  // Wh produced today
+  float house{NAN};        // W
+  float grid{NAN};         // W, > 0 = import
+  std::string agenda;      // sensor.el512_agenda events: "day|time|title;..."
+  Reading rooms[4];
+};
+
+namespace fx {
+
+// Integer hash for repeatable pseudo-random effects (lowbias32).
+inline uint32_t hash(uint32_t x) {
+  x ^= x >> 16;
+  x *= 0x7feb352d;
+  x ^= x >> 15;
+  x *= 0x846ca68b;
+  x ^= x >> 16;
+  return x;
+}
+inline uint32_t hash(uint32_t a, uint32_t b) { return hash(a * 0x9e3779b9u ^ hash(b)); }
+
+inline std::string str(const char *fmt, ...) __attribute__((format(printf, 1, 2)));
+inline std::string str(const char *fmt, ...) {
+  char buf[128];
+  va_list args;
+  va_start(args, fmt);
+  vsnprintf(buf, sizeof(buf), fmt, args);
+  va_end(args);
+  return buf;
+}
+
+inline std::string upper(std::string s) {
+  for (auto &c : s)
+    c = (char) toupper((unsigned char) c);
+  return s;
+}
+
+inline int text_width(display::Display &it, display::BaseFont *font, const char *text) {
+  int x, y, w, h;
+  it.get_text_bounds(0, 0, text, font, display::TextAlign::TOP_LEFT, &x, &y, &w, &h);
+  return w;
+}
+
+}  // namespace fx
+}  // namespace esphome::el512