chore: cleanup — remove shims, fix ruff warnings, ignore noisy rules

- Removed backward-compat shims _sanitise_for_fs / _strip_episode_from_normalised
  in domain/release/value_objects.py (zero callers).
- Fixed ruff warnings across the codebase:
    * PLW1510: explicit check=False on subprocess.run calls
    * PLC0415: promoted lazy imports to module top where no cycle exists
      (manage_subtitles, placer, qbittorrent/client, file_manager)
    * E402: fixed module-level import ordering in language_registry.py and
      subtitles/knowledge/loader.py
    * F841 / B007: removed unused locals (identifier.py)
    * C416: replaced unnecessary set comprehension with set() in
      release/knowledge.py
- Ruff config: ignore PLR0911/PLR0912 globally (noisy on mappers and
  orchestrator use-cases) and PLW0603 (intentional for the memory singleton).
- Updated tech debt memory: P1 done, ShowStatus actually complete (was a
  stale note).

alfred/infrastructure/filesystem/ffprobe.py

@@ -34,6 +34,7 @@ def probe(path: Path) -> MediaInfo | None:
             capture_output=True,
             text=True,
             timeout=30,
+            check=False,
         )
     except subprocess.TimeoutExpired:
         logger.warning("ffprobe timed out on %s", path)