Show status messages on the display

- Clock firmware: 'Connecting to WiFi...' and 'Getting the time...' at
  boot, 'Crashed!' in the OTA-only modes, and 'No WiFi' with the time
  when WiFi is down for over a minute (new DisplayController screen)
- Recovery app: shows its reason, the setup WiFi name, or its IP address,
  then powers the display off (flipdots keep the image)
- StatusScreen and drawTextLines shared by both apps
- Driver: ESP begin() no longer draws 'ESP Connected'
- Tests: No WiFi screen, short reason texts (70 total)

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

src/esp32/display/frames.cpp

@@ -3,6 +3,7 @@
 #include <stdio.h>
 
 #include "display/bitmaps.h"
+#include "display/text.h"
 #include "logic/schedule.h"
 
 // Horizontal offset that centers the 81 pixel wide clock on the 84 pixel display
@@ -31,6 +32,14 @@ void FlipdotFrames::clock(int hour, int minute)
 	_display.display();
 }
 
+void FlipdotFrames::noWifi(int hour, int minute)
+{
+	char time[6];
+	snprintf(time, sizeof(time), "%02d:%02d", hour, minute);
+	drawTextLines(_display, "No WiFi", time);
+	_display.display();
+}
+
 void FlipdotFrames::logo()
 {
 	_display.fillScreen(0);
@@ -43,13 +52,3 @@ void FlipdotFrames::blank()
 	_display.fillScreen(0);
 	_display.display();
 }
-
-void FlipdotFrames::message(const char *text)
-{
-	_display.fillScreen(0);
-	_display.setTextSize(1);
-	_display.setTextWrap(true);
-	_display.setCursor(0, 0);
-	_display.print(text);
-	_display.display();
-}

src/esp32/display/frames.h

@@ -11,11 +11,11 @@ public:
 
 	// Pikachu with a thought bubble showing HH:MM (yawning in the evening)
 	void clock(int hour, int minute) override;
+	// "No WiFi" with the time below it
+	void noWifi(int hour, int minute) override;
 	// Nintendo logo
 	void logo() override;
 	void blank() override;
-	// A line of text, e.g. while connecting
-	void message(const char *text);
 
 private:
 	BROSE9323 &_display;

src/esp32/display/status_screen.cpp

@@ -0,0 +1,31 @@
+#include "display/status_screen.h"
+
+#include <Arduino.h>
+
+#include "config.h"
+#include "display/text.h"
+
+StatusScreen::StatusScreen(BROSE9323 &display, NanoLink &nano) : _display(display), _nano(nano)
+{
+}
+
+void StatusScreen::show(const char *line1, const char *line2, bool keep_on)
+{
+	Serial.printf("Display: %s / %s\n", line1, line2 ? line2 : "");
+	_nano.on();
+	if (!_started)
+	{
+		_display.begin(&_nano.stream());
+		_display.setTiming(FLIP_TIME);
+		_started = true;
+	}
+	drawTextLines(_display, line1, line2);
+	_display.display();
+
+	if (!keep_on)
+	{
+		// The first frame after power on flips every dot, give the Nano time for that
+		delay(STATUS_FLIP_TIME);
+		_nano.off();
+	}
+}

src/esp32/display/status_screen.h

@@ -0,0 +1,21 @@
+#pragma once
+
+#include "BROSE9323.h"
+#include "nano_link/nano_link.h"
+
+// Short messages for situations outside the normal clock: booting, crashes, recovery app.
+// Used by both the clock firmware and the recovery app.
+class StatusScreen
+{
+public:
+	StatusScreen(BROSE9323 &display, NanoLink &nano);
+
+	// Power the display on, show up to two lines (TEXT_LINE_CHARS each). Unless keep_on,
+	// power off again once the dots have flipped: flipdots keep their image without power.
+	void show(const char *line1, const char *line2, bool keep_on = false);
+
+private:
+	BROSE9323 &_display;
+	NanoLink &_nano;
+	bool _started = false;
+};

src/esp32/display/text.cpp

@@ -0,0 +1,33 @@
+#include "display/text.h"
+
+#include <string.h>
+
+static const int CHAR_WIDTH = 6;
+
+static void drawCentered(BROSE9323 &display, const char *text, int y)
+{
+	int len = strlen(text);
+	if (len > TEXT_LINE_CHARS)
+		len = TEXT_LINE_CHARS;
+	char line[TEXT_LINE_CHARS + 1];
+	memcpy(line, text, len);
+	line[len] = '\0';
+
+	display.setCursor((display.width() - len * CHAR_WIDTH) / 2, y);
+	display.print(line);
+}
+
+void drawTextLines(BROSE9323 &display, const char *line1, const char *line2)
+{
+	display.fillScreen(0);
+	display.setTextSize(1);
+	display.setTextWrap(false);
+	display.setTextColor(1);
+	if (line2 == nullptr || line2[0] == '\0')
+	{
+		drawCentered(display, line1, 6); // one line: vertically centered
+		return;
+	}
+	drawCentered(display, line1, 1);
+	drawCentered(display, line2, 10);
+}

src/esp32/display/text.h

@@ -0,0 +1,10 @@
+#pragma once
+
+#include "BROSE9323.h"
+
+// Characters per line with the built-in 6x8 font on the 84 pixel wide display
+const int TEXT_LINE_CHARS = 14;
+
+// Clear the screen and draw up to two centered lines of text (line2 may be empty).
+// Does not call display().
+void drawTextLines(BROSE9323 &display, const char *line1, const char *line2);