Add a web UI to the clock firmware

- Web UI on port 80: live view of the display, choose the page (clock or
  a bitmap), bitmaps (list, show, live, edit, delete), draw / image upload
  with conversion in the browser, live mode, settings, Home Assistant
- Live view from a shadow buffer in the BROSE9323 driver (shownPixel)
- Settings in NVS with the original behaviour as defaults: schedule times,
  quarter hours, yawning Pikachu, No WiFi screen, flip time, status LED,
  Home Assistant broker (restart on change)
- Bitmaps on LittleFS; new 320 KB partition, ota slots now 1.31 MB
- DisplayController: pages, live mode, settings; app.cpp holds the objects
- README for the recovery app; docs for the web UI
- Tests: settings, time parsing, bitmap format and names, schedule with
  settings, pages and live mode (95 total)

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

src/esp32/logic/display_controller.cpp

@@ -7,6 +7,42 @@ DisplayController::DisplayController(DisplayPower &power, Frames &frames) : _pow
 {
 }
 
+void DisplayController::setSettings(const ScheduleSettings &schedule, const ClockSettings &clock)
+{
+	_schedule = schedule;
+	_clock = clock;
+	_content_revision++; // e.g. evening time changed: redraw
+}
+
+void DisplayController::setPage(Page page)
+{
+	_page = page;
+	_content_revision++;
+}
+
+void DisplayController::pageChanged()
+{
+	_content_revision++;
+}
+
+void DisplayController::showLive(uint32_t now)
+{
+	_live = true;
+	_live_since = now;
+	_content_revision++;
+}
+
+void DisplayController::stopLive()
+{
+	_live = false;
+	_content_revision++;
+}
+
+bool DisplayController::liveActive() const
+{
+	return _live;
+}
+
 void DisplayController::setClockEnabled(bool enabled)
 {
 	_clock_enabled = enabled;
@@ -36,7 +72,10 @@ void DisplayController::update(uint32_t now, bool time_valid, int hour, int minu
 		_wifi_lost = true;
 		_wifi_lost_since = now;
 	}
-	bool show_no_wifi = _wifi_lost && now - _wifi_lost_since >= NO_WIFI_SHOW_TIME;
+	bool show_no_wifi = _clock.no_wifi_screen && _wifi_lost && now - _wifi_lost_since >= NO_WIFI_SHOW_TIME;
+
+	if (_live && now - _live_since >= LIVE_TIMEOUT)
+		stopLive();
 
 	// Switched off elsewhere (power timer, Nano flashing): the Nano lost its frame
 	if (!_power.isOn())
@@ -53,12 +92,21 @@ void DisplayController::update(uint32_t now, bool time_valid, int hour, int minu
 	{
 		if (_power.isOn())
 		{
-			_showBlank();
+			_showOnce(Screen::Blank);
 			_off_timer.request(now, CLEAR_BEFORE_OFF_TIME);
 		}
 		return;
 	}
 
+	// Live mode from the web UI: shown right away, whatever the time
+	if (_live)
+	{
+		_off_timer.cancel();
+		_ensureOn();
+		_showOnce(Screen::Live);
+		return;
+	}
+
 	// Keep the boot screen until the time is known
 	if (!time_valid)
 		return;
@@ -68,64 +116,83 @@ void DisplayController::update(uint32_t now, bool time_valid, int hour, int minu
 		// The logo is only shown while the display is on; it never switches the power on
 		if (_power.isOn())
 		{
-			_showLogo();
+			_showOnce(Screen::Logo);
 			_off_timer.request(now, POWER_OFF_DELAY);
 		}
 		return;
 	}
 
-	switch (scheduleFor(hour, minute))
+	switch (scheduleFor(hour, minute, _schedule))
 	{
 	case ScheduleMode::Night:
 		if (_power.isOn())
 		{
-			_showBlank();
+			_showOnce(Screen::Blank);
 			_off_timer.request(now, POWER_OFF_DELAY);
 		}
 		break;
 	case ScheduleMode::Clock:
 		_off_timer.cancel();
-		if (!_power.isOn())
-		{
-			_power.on();
-			_screen = Screen::Unknown;
-		}
-		_showClock(hour, minute, show_no_wifi);
+		_ensureOn();
+		if (_page == Page::Clock)
+			_showClock(hour, minute, show_no_wifi);
+		else
+			_showOnce(Screen::Page);
 		break;
 	case ScheduleMode::Standby:
-		// Flipdots keep their image without power, so the last time stays visible
+		// Flipdots keep their image without power, so the last image stays visible
 		if (_power.isOn())
 			_off_timer.request(now, POWER_OFF_DELAY);
 		break;
 	}
 }
 
+void DisplayController::_ensureOn()
+{
+	if (_power.isOn())
+		return;
+	_power.on();
+	_screen = Screen::Unknown;
+}
+
 void DisplayController::_showClock(int hour, int minute, bool no_wifi)
 {
 	Screen screen = no_wifi ? Screen::NoWifi : Screen::Clock;
-	if (_screen == screen && _shown_hour == hour && _shown_minute == minute)
+	bool evening = isEvening(hour, minute, _clock);
+	if (_screen == screen && _shown_hour == hour && _shown_minute == minute && _shown_evening == evening &&
+		_shown_revision == _content_revision)
 		return;
 	if (no_wifi)
 		_frames.noWifi(hour, minute);
 	else
-		_frames.clock(hour, minute);
+		_frames.clock(hour, minute, evening);
 	_screen = screen;
 	_shown_hour = hour;
 	_shown_minute = minute;
+	_shown_evening = evening;
+	_shown_revision = _content_revision;
 }
 
-void DisplayController::_showLogo()
+// Screens without the time: only sent again when they or their content changed
+void DisplayController::_showOnce(Screen screen)
 {
-	if (_screen == Screen::Logo)
+	if (_screen == screen && _shown_revision == _content_revision)
 		return;
-	_frames.logo();
-	_screen = Screen::Logo;
-}
-
-void DisplayController::_showBlank()
-{
-	if (_screen == Screen::Blank)
-		return;
-	_frames.blank();
-	_screen = Screen::Blank;
+	switch (screen)
+	{
+	case Screen::Page:
+		_frames.page();
+		break;
+	case Screen::Live:
+		_frames.live();
+		break;
+	case Screen::Logo:
+		_frames.logo();
+		break;
+	default:
+		_frames.blank();
+		break;
+	}
+	_screen = screen;
+	_shown_revision = _content_revision;
 }