refactor!: rename somafm-tui to beefy-player

The app is now a general internet-radio player rather than a SomaFM client, so the package, console script, MPRIS identity, mpv namespaces, macOS tap names, XDG directories and docs all move to beefy-player.

Environment variables are now BEEFY_* (the old SOMAFM_* spellings are still honoured) and an existing ~/.config/somafm-tui/config.json is migrated on first run, so favourites and volume survive the rename.

The visible interface is untouched: same layout, same logo, same keys.

tests/test_art.py

@@ -3,11 +3,11 @@ from __future__ import annotations
 import pytest
 from PIL import Image
 
-from somafm_tui import artwork
-from somafm_tui.app import SomaFMApp
-from somafm_tui.widgets import art as art_widgets
-from somafm_tui.widgets.art import ArtPane, ITerm2Image, KittyImage
-from somafm_tui.widgets.stage import StagePanel
+from beefy_player import artwork
+from beefy_player.app import BeefyPlayerApp
+from beefy_player.widgets import art as art_widgets
+from beefy_player.widgets.art import ArtPane, ITerm2Image, KittyImage
+from beefy_player.widgets.stage import StagePanel
 
 
 async def _no_fetch(client, url: str) -> None:
@@ -27,7 +27,7 @@ async def test_art_pane_switches_between_image_and_mosaic(monkeypatch) -> None:
     monkeypatch.setattr(artwork, "load_cached", lambda url: None)
     monkeypatch.setattr(artwork, "fetch", _no_fetch)
 
-    app = SomaFMApp(autoplay=False, offline=True, audio=False)
+    app = BeefyPlayerApp(autoplay=False, offline=True, audio=False)
     async with app.run_test(size=(110, 40)) as pilot:
         await pilot.pause()
         pane = app.query_one(ArtPane)