fix: simplify _dioBinary in voice test page to avoid interceptor conflicts

Remove shared interceptors from the binary Dio instance to prevent
request dedup/retry interceptors from interfering with audio downloads.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

it0_app/lib/features/agent_call/presentation/pages/voice_test_page.dart

@@ -55,11 +55,10 @@ class _VoiceTestPageState extends ConsumerState<VoiceTestPage> {
     final base = ref.read(dioClientProvider);
     return Dio(BaseOptions(
       baseUrl: base.options.baseUrl,
-      headers: Map.from(base.options.headers),
       connectTimeout: const Duration(seconds: 30),
       receiveTimeout: const Duration(seconds: 120),
       responseType: ResponseType.bytes,
-    ))..interceptors.addAll(base.interceptors);
+    ));
   }
 
   Dio get _dioJson => ref.read(dioClientProvider);