Fix dense images on the Nano and the off image in slow mode

- Nano: B data is drawn fast enough for the serial line. A hex digit arrives
  every 87 us; with a division and four drawPixel() calls per digit a lit
  digit took about 105 us, so dense frames (all yellow, the panda bitmap)
  overflowed the 64 byte receive buffer: frames not shown or wrong, "Line
  too long", frame check repairs that failed the same way. Now the parser
  counts columns and rows and BROSE9323::drawDots() sets the 4 dots
  (about 20 us).
- ESP32: Power off and the start of the night draw the off image also when
  slow mode had the power off already (it powers on for it, once)
- Tests: drawDots() against drawPixel(), off image in slow mode
- Version 2.19.3

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

src/esp32/logic/display_controller.cpp

@@ -103,8 +103,9 @@ void DisplayController::update(uint32_t now, bool time_valid, const LocalTime &t
 
 	if (!_power_enabled)
 	{
-		if (_power.isOn())
+		if (_power.isOn() || _off_needed)
 		{
+			_ensureOn();
 			_showOnce(Screen::Off);
 			_off_timer.request(now, CLEAR_BEFORE_OFF_TIME + _effect_time);
 		}
@@ -129,8 +130,9 @@ void DisplayController::update(uint32_t now, bool time_valid, const LocalTime &t
 	case ScheduleMode::Night:
 		_slow_last = -1; // the morning starts with an update
 		_slow_keep = false;
-		if (_power.isOn())
+		if (_power.isOn() || _off_needed)
 		{
+			_ensureOn();
 			_showOnce(Screen::Off);
 			_off_timer.request(now, POWER_OFF_DELAY);
 		}
@@ -209,6 +211,7 @@ void DisplayController::_showDynamic(uint32_t now, const LocalTime &time, bool n
 		_dynamic_due = now + wait;
 	}
 	_screen = screen;
+	_off_needed = true;
 	_shown_hour = time.hour;
 	_shown_minute = time.minute;
 	_shown_revision = _content_revision;
@@ -232,5 +235,6 @@ void DisplayController::_showOnce(Screen screen)
 		break;
 	}
 	_screen = screen;
+	_off_needed = screen != Screen::Off;
 	_shown_revision = _content_revision;
 }

src/esp32/logic/display_controller.h

@@ -109,6 +109,9 @@ private:
 	bool _power_enabled = true;
 
 	Screen _screen = Screen::Unknown;
+	// The dots show a frame other than the off screen, also while the power is off (slow
+	// mode): Power off and night power on to draw the off screen
+	bool _off_needed = false;
 	int _shown_hour = -1;
 	int _shown_minute = -1;
 	uint32_t _dynamic_due = 0; // millis() when a moving dynamic page is drawn again