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.h

@@ -2,6 +2,9 @@
 
 #include <stdint.h>
 
+#include "logic/builtin_pages.h"
+#include "logic/page.h"
+
 // Everything that can be changed in the web UI. Stored in NVS (system/settings_store),
 // the defaults are the original behaviour. Pure logic, tested in test/test_esp32.
 //
@@ -18,9 +21,7 @@ struct ScheduleSettings
 
 struct ClockSettings
 {
-	bool evening_enabled = true;    // yawning Pikachu in the evening
-	uint16_t evening_start = 17 * 60;
-	bool no_wifi_screen = true;     // "No WiFi" instead of the clock when WiFi is down
+	bool no_wifi_screen = true;     // "No WiFi" instead of a dynamic page when WiFi is down
 };
 
 struct HomeAssistantSettings
@@ -30,6 +31,9 @@ struct HomeAssistantSettings
 	uint16_t port = 1883;
 	char user[32] = "";
 	char password[64] = "";
+	// Values for the dynamic pages, read over Home Assistant's REST API (net/ha_api)
+	char api_url[96] = "";          // empty: http://<MQTT broker>:8123
+	char token[256] = "";           // long-lived access token (HA user profile, Security)
 };
 
 // How the Nano drives the dots (besides the flip time). Sent to the Nano, which keeps
@@ -50,25 +54,23 @@ struct DriveSettings
 	bool effect_small_only = false; // big changes (a new page) appear instantly
 };
 
-// What is shown during the day: "clock" or the name of a bitmap
-const int PAGE_NAME_SIZE = 25;
-#define PAGE_CLOCK "clock"
+// What is shown during the day: the name of a dynamic page (logic/page.h) or a bitmap.
+// Both share one namespace. When it is gone, the built-in Clock page is shown.
+#define DEFAULT_PAGE BUILTIN_PAGE_CLOCK
 // What is left on the dots when the display switches off: empty = blank, or a bitmap name
 #define OFF_PAGE_BLANK ""
 
 struct Settings
 {
-	char page[PAGE_NAME_SIZE] = PAGE_CLOCK;
+	char page[PAGE_NAME_SIZE] = DEFAULT_PAGE;
 	ScheduleSettings schedule;
 	ClockSettings clock;
 	HomeAssistantSettings home_assistant;
 	uint16_t flip_time = 225; // flip pulse length in us, sent to the Nano
 	bool status_led = true;
-	// Added in settings version 2: keep it last, the fields before it are read from
-	// version 1 records (system/settings_store.cpp)
 	char off_page[PAGE_NAME_SIZE] = OFF_PAGE_BLANK;
-	// Added in version 3
 	DriveSettings drive;
+	// New fields go here, at the end (see system/settings_store.cpp)
 };
 
 // How long a new frame can take to appear on the dots in ms (0 when instant)