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/display/status_screen.h

@@ -14,8 +14,12 @@ public:
 	// 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);
 
+	// Flip time sent to the Nano with the first message (default FLIP_TIME)
+	void setFlipTime(uint16_t flip_time);
+
 private:
 	BROSE9323 &_display;
 	NanoLink &_nano;
 	bool _started = false;
+	uint16_t _flip_time;
 };