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/config.h

@@ -41,6 +41,8 @@ const uint32_t CLEAR_BEFORE_OFF_TIME = 1000;
 const uint32_t STATUS_FLIP_TIME = 2000;
 // WiFi down this long while the clock runs: show "No WiFi" with the time instead
 const uint32_t NO_WIFI_SHOW_TIME = 60000;
+// Live mode of the web UI ends this long after the last image was sent
+const uint32_t LIVE_TIMEOUT = 30UL * 60 * 1000;
 // Power off this long after the display is no longer needed (night, standby, logo)
 const uint32_t POWER_OFF_DELAY = 30000;