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.

tools/voice_mode.py

@@ -636,7 +636,13 @@ def play_audio_file(file_path: str) -> bool:
                 sample_rate = wf.getframerate()
 
             sd.play(audio_data, samplerate=sample_rate)
-            sd.wait()
+            # sd.wait() calls Event.wait() without timeout — hangs forever if
+            # the audio device stalls.  Poll with a ceiling and force-stop.
+            duration_secs = len(audio_data) / sample_rate
+            deadline = time.monotonic() + duration_secs + 2.0
+            while sd.get_stream() and sd.get_stream().active and time.monotonic() < deadline:
+                time.sleep(0.01)
+            sd.stop()
             return True
         except (ImportError, OSError):
             pass  # audio libs not available, fall through to system players