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/main.cpp

@@ -1,27 +1,20 @@
-// ESP32 firmware: decides what the flipdot display shows (clock, Home Assistant switches)
-// and sends it to the Nano, which drives the panels. See README.md.
+// ESP32 firmware: decides what the flipdot display shows (clock, bitmaps, web UI, Home
+// Assistant) and sends it to the Nano, which drives the panels. See README.md.
+// The objects and the actions on them are in app.cpp; this file only sets the order.
 
 #include <Arduino.h>
 #include <time.h>
 
-#include "BROSE9323.h"
+#include "app.h"
 #include "config.h"
-#include "display/frames.h"
-#include "display/status_screen.h"
-#include "logic/display_controller.h"
+#include "display/bitmap_store.h"
 #include "logic/status_led.h"
 #include "nano_link/nano_flash_bridge.h"
-#include "nano_link/nano_link.h"
 #include "net/home_assistant.h"
 #include "net/wifi_ota.h"
 #include "system/boot_target.h"
 #include "system/firmware_guard.h"
-
-NanoLink nano(Serial2, NANO_RX_PIN, NANO_TX_PIN, RELAY_PIN, NANO_RESET_PIN);
-BROSE9323 display(DISPLAY_WIDTH, DISPLAY_HEIGHT, PANEL_WIDTH);
-FlipdotFrames frames(display);
-StatusScreen status(display, nano);
-DisplayController controller(nano, frames);
+#include "web/web_ui.h"
 
 // Flashing the Nano over WiFi: restart it into its bootloader, switch it off afterwards.
 // The controller then powers it on again with the new firmware.
@@ -39,6 +32,9 @@ void setup()
 	// Decided first, before anything that could crash
 	BootMode boot_mode = firmwareGuardBegin();
 
+	bitmapStoreBegin();
+	appLoadSettings();
+
 	if (boot_mode == BootMode::Normal)
 		status.show("Connecting", "to WiFi...", true);
 	wifiBegin(); // starts the recovery app when it fails
@@ -66,7 +62,8 @@ void setup()
 	status.show("Getting", "the time...", true);
 
 	configTzTime(TIMEZONE, NTP_SERVER);
-	homeAssistantBegin(controller);
+	homeAssistantBegin(controller, appSettings().home_assistant);
+	webUiBegin();
 
 	firmwareGuardStartWatchdog();
 }
@@ -80,6 +77,8 @@ void loop()
 
 	homeAssistantSetFirmwareStatus(firmwareGuardStatus());
 	homeAssistantLoop();
+	webUiLoop();
+	appLoop();
 
 	// While the Nano is being flashed, nothing else may talk to it
 	if (flashBridge.handle())
@@ -89,5 +88,6 @@ void loop()
 	bool time_valid = getLocalTime(&now, 0);
 	controller.update(millis(), time_valid, now.tm_hour, now.tm_min, wifiConnected());
 
-	digitalWrite(LED_PIN, statusLedLevel(millis(), wifiConnected(), nano.isOn()));
+	bool led = appSettings().status_led && statusLedLevel(millis(), wifiConnected(), nano.isOn());
+	digitalWrite(LED_PIN, led);
 }