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/settings.cpp

@@ -12,8 +12,7 @@ static bool terminated(const char *text, int size)
 
 const char *validateSettings(const Settings &s)
 {
-	if (!terminated(s.page, sizeof(s.page)) ||
-		(strcmp(s.page, PAGE_CLOCK) != 0 && !validBitmapName(s.page)))
+	if (!terminated(s.page, sizeof(s.page)) || !validBitmapName(s.page))
 		return "Unknown page";
 	if (!terminated(s.off_page, sizeof(s.off_page)) || (s.off_page[0] && !validBitmapName(s.off_page)))
 		return "Unknown off image";
@@ -24,9 +23,6 @@ const char *validateSettings(const Settings &s)
 	if (t.day_start > t.late_start || t.late_start > t.night_start)
 		return "The times must be in order: day start, late evening, night";
 
-	if (s.clock.evening_start >= MINUTES_PER_DAY)
-		return "The evening must start before 24:00";
-
 	if (s.flip_time < SETTINGS_FLIP_TIME_MIN || s.flip_time > SETTINGS_FLIP_TIME_MAX)
 		return "The flip time must be between 50 and 2000 us";
 
@@ -42,10 +38,13 @@ const char *validateSettings(const Settings &s)
 
 	const HomeAssistantSettings &ha = s.home_assistant;
 	if (!terminated(ha.host, sizeof(ha.host)) || !terminated(ha.user, sizeof(ha.user)) ||
-		!terminated(ha.password, sizeof(ha.password)))
+		!terminated(ha.password, sizeof(ha.password)) || !terminated(ha.api_url, sizeof(ha.api_url)) ||
+		!terminated(ha.token, sizeof(ha.token)))
 		return "Home Assistant text too long";
 	if (ha.port == 0)
 		return "Invalid MQTT port";
+	if (ha.api_url[0] && strncmp(ha.api_url, "http://", 7) != 0)
+		return "The Home Assistant URL must start with http:// (https is not supported)";
 
 	return nullptr;
 }