Add Volcengine support for TTS and ASR services

- Introduced Volcengine as a new provider for both TTS and ASR services.
- Updated configuration files to include Volcengine-specific parameters such as app_id, resource_id, and uid.
- Enhanced the ASR service to support streaming mode with Volcengine's API.
- Modified existing tests to validate the integration of Volcengine services.
- Updated documentation to reflect the addition of Volcengine as a supported provider for TTS and ASR.
- Refactored service factory to accommodate Volcengine alongside existing providers.

engine/tests/test_backend_adapters.py

@@ -227,6 +227,62 @@ async def test_with_backend_url_uses_backend_for_assistant_config(monkeypatch, t
     assert payload["assistant"]["systemPrompt"] == "backend prompt"
 
 
+def test_translate_agent_schema_maps_volcengine_fields():
+    payload = {
+        "agent": {
+            "tts": {
+                "provider": "volcengine",
+                "api_key": "tts-key",
+                "api_url": "https://openspeech.bytedance.com/api/v3/tts/unidirectional",
+                "app_id": "app-123",
+                "resource_id": "seed-tts-2.0",
+                "uid": "caller-1",
+                "voice": "zh_female_shuangkuaisisi_moon_bigtts",
+                "speed": 1.1,
+            },
+            "asr": {
+                "provider": "volcengine",
+                "api_key": "asr-key",
+                "api_url": "wss://openspeech.bytedance.com/api/v3/sauc/bigmodel",
+                "model": "bigmodel",
+                "app_id": "app-123",
+                "resource_id": "volc.bigasr.sauc.duration",
+                "uid": "caller-1",
+                "request_params": {
+                    "end_window_size": 800,
+                    "force_to_speech_time": 1000,
+                },
+            },
+        }
+    }
+
+    translated = LocalYamlAssistantConfigAdapter._translate_agent_schema("assistant_demo", payload)
+    assert translated is not None
+    assert translated["services"]["tts"] == {
+        "provider": "volcengine",
+        "apiKey": "tts-key",
+        "baseUrl": "https://openspeech.bytedance.com/api/v3/tts/unidirectional",
+        "voice": "zh_female_shuangkuaisisi_moon_bigtts",
+        "appId": "app-123",
+        "resourceId": "seed-tts-2.0",
+        "uid": "caller-1",
+        "speed": 1.1,
+    }
+    assert translated["services"]["asr"] == {
+        "provider": "volcengine",
+        "model": "bigmodel",
+        "apiKey": "asr-key",
+        "baseUrl": "wss://openspeech.bytedance.com/api/v3/sauc/bigmodel",
+        "appId": "app-123",
+        "resourceId": "volc.bigasr.sauc.duration",
+        "uid": "caller-1",
+        "requestParams": {
+            "end_window_size": 800,
+            "force_to_speech_time": 1000,
+        },
+    }
+
+
 @pytest.mark.asyncio
 async def test_backend_mode_disabled_uses_local_assistant_config_even_with_url(monkeypatch, tmp_path):
     class _FailIfCalledClientSession: