Remove dead code

- wire.with_figure: the device uses dataclasses.replace directly.
- DeviceConnected/DeviceDisconnected: emitted, never subscribed to, and a duplicate
  of ConnectionChanged(target="firmware").
- ScreenService.toggle(): never called.
- GET /api/lirc (LircConfigOut, api.lircConfig): no front-end reads it.
- POST /api/volume's delta_percent (api.nudgeVolume): no front-end sends it.
- LibraryCache.shrink_stored_covers: a one-off migration that re-read every cover
  header on every scan. _INDEX_VERSION 7 rebuilds any cache that could still need it.
- Firmware: the MFRC522 library and its unused globals (lib/nfc/rc522.c is the
  driver in use), and mfrc_version.h, a reader test sketch nothing included.

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

esp-firmware/platformio.ini

@@ -25,7 +25,6 @@ upload_port = /dev/ttyUSB0
 monitor_speed = 115200
 build_src_filter = +<*> -<host_test.cpp>
 lib_deps = 
-	miguelbalboa/MFRC522@1.4.12
 	bxparks/AceButton@1.10.1
 
 [env:native]