Add dynamic pages with clock, date, Home Assistant values and fonts

The hardcoded clock is now the built-in dynamic page "Clock". A dynamic page
has a background bitmap per time of day and up to 8 elements (clock, date,
Home Assistant value, text), each with position, alignment, font and overlay.
Pages are drawn on the ESP32, also for the web previews.

- Pages tab in the web UI: page editor with drag and drop, font upload
  (TTF/OTF converted in the browser to the FDF1 dot font format)
- Built-in fonts Small, Normal, Large and Full height (generated by
  tools/make_builtin_fonts.py), built-in bitmaps Pikachu and Pikachu yawning
- Home Assistant values over the REST API (URL and token in the HA tab)
- Settings version 4: evening settings removed (now time slots of the Clock
  page), old records are converted
- HA Mode dropdown lists the dynamic pages and bitmaps

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

src/esp32/logic/builtin_fonts.h

@@ -0,0 +1,27 @@
+#pragma once
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "logic/font.h"
+
+// The built-in fonts of the dynamic pages (data in builtin_fonts.cpp, generated by
+// tools/make_builtin_fonts.py): "Small" (3x5), "Normal" (5x7, the old clock font),
+// "Large" (Normal x 2) and "Full height" (19 dot digits, only 0-9 : . - and space).
+
+struct BuiltinFont
+{
+	const char *name;
+	const uint8_t *data;
+	size_t size;
+	uint8_t scale;
+};
+
+extern const BuiltinFont BUILTIN_FONTS[];
+extern const int BUILTIN_FONT_COUNT;
+
+#define FONT_NORMAL_NAME "Normal"
+
+// nullptr when there is no built-in font with this name (compared without case)
+const BuiltinFont *findBuiltinFont(const char *name);
+Font builtinFont(const BuiltinFont &font);