Fix torrent post-import category follow-ups and clear the lint backlog (#1154)

rTorrent set_category and remove now uppercase the info hash, which
reaches us lowercase while rTorrent's XML-RPC lookups are case
sensitive. remove() had this bug before #1148, making
PROWLARR_TORRENT_ACTION=remove a silent no-op for rTorrent.

Transmission set_category appends the post-import label instead of
replacing the whole label list. The unsupported-client path in
post_process_cleanup logs at debug instead of warning, so Real-Debrid
and AllDebrid users stop seeing a warning on every successful import.

The Real-Debrid and AllDebrid clients now follow the conventions used by
the other clients (_raise_runtime_error helpers, narrow error tuples,
ClassVar, Path.open), and register_client is generic over a TypeVar
bound to DownloadClient so decorated classes keep their concrete type.
make fix and the lint, format and typecheck targets all pass.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

tests/prowlarr/test_source.py

@@ -776,6 +776,8 @@ class TestMamLanguageCoverage:
         }
         for tag, expected in cases.items():
             assert _extract_mam_language(f"Book [{tag} / M4B]") == expected, tag
+
+
 class _MultiIndexerClient:
     """Torznab client where each indexer entry returns its own result set.