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>

python-backend/tests/test_remote_api.py

@@ -65,13 +65,6 @@ async def album_id(sim: Simulation, title: str) -> str:
     return next(a.id for a in sim.app.library.albums if a.title == title)
 
 
-# ------------------------------------------------------------------------------ lirc
-
-
-async def test_lirc_is_a_404_when_unconfigured(client: httpx2.AsyncClient) -> None:
-    assert (await client.get("/api/lirc")).status_code == 404
-
-
 # --------------------------------------------------------------------------- reading