Add HA dropdowns, off image, flip fixes and refresh effects

Home Assistant: remove the Clock switch (its entity is deleted on connect),
add an IP sensor and Mode / Off image dropdowns whose options follow the
saved bitmaps. Remove the built-in "Nintendo border" bitmap.

Off image: a bitmap (or blank) left on the dots when the display switches off.

Nano: pause after each flip pulse and repeat pulses for changed dots, both
stored in EEPROM (G/N commands). Refresh effects (E command): instant,
sparkle, wipe, rain, from the middle out, diagonal, spiral, flip all then
reveal, push and random, optionally only for small changes. Effects run in
steps from loop() so serial input keeps flowing.

Web UI: flip settings, refresh effect and test patterns under Settings; the
System tab shows why the ESP32 last restarted. Settings records from
versions 1 and 2 are migrated. Firmware 2.3.0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/esp32/config.h

@@ -43,7 +43,7 @@ const uint32_t STATUS_FLIP_TIME = 2000;
 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)
+// Power off this long after the display is no longer needed (night, standby)
 const uint32_t POWER_OFF_DELAY = 30000;
 
 // ---------------------------------------------------------------------------
@@ -95,7 +95,7 @@ const uint32_t SETUP_AP_DELAY = 20000;        // open the AP when WiFi fails thi
 const uint32_t WIFI_CONNECT_TIMEOUT = 30000;
 const uint32_t WIFI_RESTART_TIME = 10UL * 60 * 1000;
 
-#define FIRMWARE_VERSION "2.1.0"
+#define FIRMWARE_VERSION "2.3.0"
 
 // Home Assistant device id (do not change: Home Assistant's entities are linked to it)
 const uint8_t HA_DEVICE_ID[] = {0x34, 0x86, 0x5d, 0x3a, 0x08, 0x28};