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/net/home_assistant.h

@@ -4,8 +4,11 @@
 #include "logic/settings.h"
 
 // Home Assistant integration over MQTT (with discovery):
-//   FlipDot Display Clock     switch: on = clock, off = Nintendo logo
-//   FlipDot Display Power     switch: off = clear the display and switch it off
+//   FlipDot Display Power     switch: off = draw the off image and switch the display off
+//   FlipDot Display Mode      select: the page shown during the day ("Clock" or a bitmap)
+//   FlipDot Display Off image select: left on the dots when the display switches off
+//                                     ("Blank" or a bitmap)
+//   FlipDot Display IP        sensor: the IP address
 //   FlipDot Display Firmware  sensor: version and health, e.g. "2.1.0, ok, 0 crashes, ..."
 //   FlipDot Display Recovery  button: restart into the recovery app (for 10 minutes)
 //