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>

lib/BROSE9323/BROSE9323.cpp

@@ -70,6 +70,8 @@ void BROSE9323::display(bool force)
 #ifdef ESPSERIAL
   stream->print("D\n");
   stream->flush();
+  // Shadow copy of what the dots show now (for the web UI)
+  memcpy(_old_buffer, _new_buffer, _buffer_size);
 #else
   if (_direct_mode)
     return;
@@ -113,7 +115,20 @@ void BROSE9323::drawPixel(int16_t x, int16_t y, uint16_t color)
 #ifdef ESPSERIAL
   if (y >= height() || y < 0 || x >= width() || x < 0)
     return;
-    
+
+  // Shadow copy for the web UI; S (direct mode) is visible right away
+  if (color)
+    _new_buffer[y * _buffer_width + x / 8] |= 1 << (x & 7);
+  else
+    _new_buffer[y * _buffer_width + x / 8] &= ~(1 << (x & 7));
+  if (_direct_mode)
+  {
+    if (color)
+      _old_buffer[y * _buffer_width + x / 8] |= 1 << (x & 7);
+    else
+      _old_buffer[y * _buffer_width + x / 8] &= ~(1 << (x & 7));
+  }
+
   char s[10];
   sprintf(s, "%c%02x%02x%d\n", _direct_mode ? 'S' : 's', x, y, (bool)color);
   stream->print(s);
@@ -162,6 +177,7 @@ void BROSE9323::drawPixel(int16_t x, int16_t y, uint16_t color)
 void BROSE9323::fillScreen(uint16_t color)
 {
 #ifdef ESPSERIAL
+  memset(_new_buffer, color ? 0xFF : 0x00, _buffer_size);
   stream->print(color ? "F1\n" : "F0\n");
 #else
   memset(_new_buffer, color ? 0xFF : 0x00, _buffer_size);
@@ -309,4 +325,14 @@ size_t BROSE9323::print(const char *ifsh)
   ifsh = temp.c_str();
 
   return Adafruit_GFX::print(ifsh);
-}
+}
+bool BROSE9323::shownPixel(int16_t x, int16_t y) const
+{
+  if (y >= height() || y < 0 || x >= width() || x < 0)
+    return false;
+#if defined(__AVR_ATmega168P__) || defined(__AVR_ATmega168PB__) || defined(__AVR_ATmega168__)
+  return _new_buffer[y * _buffer_width + x / 8] & (1 << (x & 7));
+#else
+  return _old_buffer[y * _buffer_width + x / 8] & (1 << (x & 7));
+#endif
+}

lib/BROSE9323/BROSE9323.h

@@ -87,5 +87,7 @@ public:
     void printBuffer(void);
 #endif
     size_t print(const char *ifsh);
+    // State of a dot as of the last display() call (ESP32: shadow copy for the web UI)
+    bool shownPixel(int16_t x, int16_t y) const;
 };
 #endif //BROSE9323_H