fix: address PR review round 4 — remove web UI, fix audio/import/interface issues

Remove web UI gateway (web.py, tests, docs, toolset, env vars, Platform.WEB
enum) per maintainer request — Nous is building their own official chat UI.

Fix 1: Replace sd.wait() with polling pattern in play_audio_file() to prevent
indefinite hang when audio device stalls (consistent with play_beep()).

Fix 2: Use importlib.util.find_spec() for faster_whisper/openai availability
checks instead of module-level imports that trigger heavy native library
loading (CUDA/cuDNN) at import time.

Fix 3: Remove inspect.signature() hack in _send_voice_reply() — add **kwargs
to Telegram send_voice() so all adapters accept metadata uniformly.

Fix 4: Make session loading resilient to removed platform enum values — skip
entries with unknown platforms instead of crashing the entire gateway.

gateway/session.py

@@ -383,7 +383,11 @@ class SessionStore:
                 with open(sessions_file, "r", encoding="utf-8") as f:
                     data = json.load(f)
                     for key, entry_data in data.items():
-                        self._entries[key] = SessionEntry.from_dict(entry_data)
+                        try:
+                            self._entries[key] = SessionEntry.from_dict(entry_data)
+                        except (ValueError, KeyError):
+                            # Skip entries with unknown/removed platform values
+                            continue
             except Exception as e:
                 print(f"[gateway] Warning: Failed to load sessions: {e}")