feat(providers): add a pluggable station-catalogue seam

The app now holds one RadioProvider and asks it for stations, song history and stream URLs instead of importing SomaFM's HTTP client directly.

- models.py: provider-neutral Song/Station plus the shared parsers every catalogue needs (Station.provider/.uid keep ids unique once there is more than one).
- providers/base.py: the RadioProvider interface and the toolkit it needs in practice - httpx client factory, .pls/.m3u resolution with an 8h disk cache, and a default stream_candidates() strategy.
- providers/somafm/: everything SomaFM-specific (channels.json, songs/<id>.json, PLS layout, guessed icecast mirrors) behind SomaFMProvider.
- providers/__init__.py: registry, get_provider() and --provider, remembered in the config file.

Widgets render branding, splash copy and the help credits from the active provider, so a second catalogue needs no UI changes; with SomaFM selected the screen is byte-identical to before.

beefy_player/__main__.py

@@ -6,16 +6,23 @@ import argparse
 import asyncio
 from collections.abc import Sequence
 
-from . import __version__, api
-from .fallback import fallback_channels
+from . import __version__
+from .providers import available_providers, get_provider
+from .providers.base import make_client
 from .spectrum import SOURCE_MODES
 
 
 def _build_parser() -> argparse.ArgumentParser:
     parser = argparse.ArgumentParser(
-        prog="somafm-tui",
-        description="A flashy terminal radio for somafm.com — live spectrum, "
-        "song history and desktop media integration.",
+        prog="beefy-player",
+        description="Beefy Player — a flashy terminal player for internet "
+        "radio: live spectrum, song history and desktop media integration.",
+    )
+    parser.add_argument(
+        "--provider",
+        choices=available_providers(),
+        metavar="ID",
+        help="station catalogue to use (default: the one in the config file)",
     )
     parser.add_argument("--station", metavar="ID", help="station id to select")
     parser.add_argument(
@@ -72,13 +79,15 @@ def _build_parser() -> argparse.ArgumentParser:
     return parser
 
 
-def _list_stations(offline: bool) -> int:
-    stations = api.load_cached_channels()
+def _list_stations(offline: bool, provider_id: str | None = None) -> int:
+    provider = get_provider(provider_id)
+    stations = provider.load_cached_stations()
     if not stations and not offline:
+
         async def load():
-            client = api.make_client()
+            client = make_client(provider.user_agent)
             try:
-                return await api.fetch_channels(client)
+                return await provider.fetch_stations(client)
             finally:
                 await client.aclose()
 
@@ -87,7 +96,8 @@ def _list_stations(offline: bool) -> int:
         except Exception:
             stations = []
     if not stations:
-        stations = api.parse_channels({"channels": fallback_channels()})
+        stations = provider.fallback_stations()
+    print(f"# {provider.name} ({provider.id}) — {provider.station_source}")
     for station in sorted(stations, key=lambda item: item.title.casefold()):
         print(f"{station.id:<20} {station.title}")
     return 0
@@ -103,13 +113,14 @@ def main(argv: Sequence[str] | None = None) -> int:
         return 0
 
     if args.list:
-        return _list_stations(args.offline)
+        return _list_stations(args.offline, args.provider)
 
     # Import the app lazily so --list/--version do not probe the terminal for
     # image protocols.
-    from .app import SomaFMApp
+    from .app import BeefyPlayerApp
 
-    app = SomaFMApp(
+    app = BeefyPlayerApp(
+        provider=args.provider,
         autoplay=args.autoplay,
         station_id=args.station,
         volume=args.volume,