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/app.h

@@ -7,6 +7,8 @@
 #include "display/frames.h"
 #include "display/status_screen.h"
 #include "logic/display_controller.h"
+#include "logic/local_time.h"
+#include "logic/page.h"
 #include "logic/settings.h"
 #include "nano_link/nano_link.h"
 
@@ -20,20 +22,31 @@ extern DisplayController controller;
 const Settings &appSettings();
 void appLoadSettings();
 // Validates, stores and applies. Returns nullptr or an error message. Sets
-// restart_needed when the change only works after a restart (Home Assistant).
+// restart_needed when the change only works after a restart (Home Assistant MQTT).
 const char *appSaveSettings(const Settings &settings, bool &restart_needed);
 
-// The page shown during the day: PAGE_CLOCK or a bitmap name (stored in the settings)
+// The page shown during the day: a dynamic page or a bitmap (stored in the settings)
 const char *appSelectPage(const char *name);
 // Left on the dots when the display switches off: OFF_PAGE_BLANK or a bitmap name
 const char *appSelectOffPage(const char *name);
-// A bitmap was saved or deleted: redraw when it is the current page or off image
-void appBitmapChanged(const char *name);
+
+// Bitmaps, dynamic pages and fonts: stored, and the display redrawn when it shows them.
+// Bitmaps and pages share one namespace; what a page uses can't be deleted. All return
+// nullptr or an error message.
+const char *appSaveBitmap(const char *name, const uint8_t *bitmap);
+const char *appDeleteBitmap(const char *name);
+const char *appSavePage(const char *name, const DynamicPage &page);
+const char *appDeletePage(const char *name);
+const char *appSaveFont(const char *name, const uint8_t *data, size_t size);
+const char *appDeleteFont(const char *name);
 
 // Live mode of the web UI
 void appShowLive(const uint8_t *bitmap);
 void appStopLive();
 
+// The local time; false until it is synced over NTP
+bool appLocalTime(LocalTime &time);
+
 // Restart the ESP32 after `delay_ms` (so a web response can still be sent)
 void appRestartLater(uint32_t delay_ms);
 void appLoop();