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/config.h

@@ -45,6 +45,10 @@ const uint32_t NO_WIFI_SHOW_TIME = 60000;
 const uint32_t LIVE_TIMEOUT = 30UL * 60 * 1000;
 // Power off this long after the display is no longer needed (night, standby)
 const uint32_t POWER_OFF_DELAY = 30000;
+// Home Assistant values on dynamic pages (net/ha_api): read this often, and the HTTP
+// timeout (a read blocks loop() for at most about twice this)
+const uint32_t HA_POLL_INTERVAL = 60000;
+const uint32_t HA_HTTP_TIMEOUT = 1500;
 
 // ---------------------------------------------------------------------------
 // Flashing the Nano over WiFi (see README.md, pio run -e nano_ota -t upload)
@@ -95,7 +99,7 @@ const uint32_t SETUP_AP_DELAY = 20000;        // open the AP when WiFi fails thi
 const uint32_t WIFI_CONNECT_TIMEOUT = 30000;
 const uint32_t WIFI_RESTART_TIME = 10UL * 60 * 1000;
 
-#define FIRMWARE_VERSION "2.3.0"
+#define FIRMWARE_VERSION "2.4.0"
 
 // Home Assistant device id (do not change: Home Assistant's entities are linked to it)
 const uint8_t HA_DEVICE_ID[] = {0x34, 0x86, 0x5d, 0x3a, 0x08, 0x28};