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.h

@@ -3,6 +3,7 @@
 #include <stdint.h>
 
 #include "logic/power_timer.h"
+#include "logic/settings.h"
 
 // Power for the panels and the Nano (implemented by NanoLink)
 class DisplayPower
@@ -18,22 +19,44 @@ public:
 class Frames
 {
 public:
-	virtual void clock(int hour, int minute) = 0;
+	virtual void clock(int hour, int minute, bool evening) = 0;
 	// Shown instead of the clock while WiFi is down (the time keeps running without it)
 	virtual void noWifi(int hour, int minute) = 0;
+	// The bitmap selected as page
+	virtual void page() = 0;
+	// The image sent from the web UI's live mode
+	virtual void live() = 0;
 	virtual void logo() = 0;
 	virtual void blank() = 0;
 };
 
-// Decides what the display shows and when it is powered, based on the time and the two
-// Home Assistant switches. A frame is only sent when it changes. Pure logic, tested in
-// test/test_esp32.
+enum class Page : uint8_t
+{
+	Clock,  // Pikachu with the time
+	Bitmap, // a bitmap (FlipdotFrames holds which one)
+};
+
+// Decides what the display shows and when it is powered, based on the time, the settings,
+// the Home Assistant switches and the web UI. A frame is only sent when it changes. Pure
+// logic, tested in test/test_esp32.
 class DisplayController
 {
 public:
 	DisplayController(DisplayPower &power, Frames &frames);
 
-	// Home Assistant "FlipDot Display Clock" switch: off shows the logo instead of the clock
+	void setSettings(const ScheduleSettings &schedule, const ClockSettings &clock);
+
+	// What is shown during the day. Call pageChanged() when the bitmap itself changed.
+	void setPage(Page page);
+	void pageChanged();
+
+	// Live mode: show Frames::live() now, whatever the time, until stopLive() or
+	// LIVE_TIMEOUT after the last showLive()
+	void showLive(uint32_t now);
+	void stopLive();
+	bool liveActive() const;
+
+	// Home Assistant "FlipDot Display Clock" switch: off shows the logo instead of the page
 	void setClockEnabled(bool enabled);
 	// Home Assistant "FlipDot Display Power" switch: off clears the display and powers it off
 	void setPowerEnabled(bool enabled);
@@ -51,6 +74,8 @@ private:
 		Unknown, // nothing sent since the last power on
 		Clock,
 		NoWifi,
+		Page,
+		Live,
 		Logo,
 		Blank,
 	};
@@ -59,17 +84,27 @@ private:
 	Frames &_frames;
 	PowerTimer _off_timer;
 
+	ScheduleSettings _schedule;
+	ClockSettings _clock;
+	Page _page = Page::Clock;
+
 	bool _clock_enabled = true;
 	bool _power_enabled = true;
 
 	Screen _screen = Screen::Unknown;
 	int _shown_hour = -1;
 	int _shown_minute = -1;
+	bool _shown_evening = false;
+	uint32_t _content_revision = 0; // changed page, bitmap or live image
+	uint32_t _shown_revision = 0;
+
+	bool _live = false;
+	uint32_t _live_since = 0;
 
 	bool _wifi_lost = false;
 	uint32_t _wifi_lost_since = 0;
 
+	void _ensureOn();
 	void _showClock(int hour, int minute, bool no_wifi);
-	void _showLogo();
-	void _showBlank();
+	void _showOnce(Screen screen);
 };