feat: Implement Dify LLM provider and update related configurations and tests

engine/tests/test_llm_factory_modes.py

@@ -0,0 +1,32 @@
+from providers.factory.default import DefaultRealtimeServiceFactory
+from providers.llm.dify import DifyLLMService
+from providers.llm.openai import OpenAILLMService
+from runtime.ports import LLMServiceSpec
+
+
+def test_create_llm_service_dify_returns_dify_provider():
+    factory = DefaultRealtimeServiceFactory()
+    service = factory.create_llm_service(
+        LLMServiceSpec(
+            provider="dify",
+            model="dify",
+            api_key="test-key",
+            base_url="https://dify.example/v1",
+        )
+    )
+
+    assert isinstance(service, DifyLLMService)
+
+
+def test_create_llm_service_openai_returns_openai_provider():
+    factory = DefaultRealtimeServiceFactory()
+    service = factory.create_llm_service(
+        LLMServiceSpec(
+            provider="openai",
+            model="gpt-4o-mini",
+            api_key="test-key",
+            base_url="https://api.openai.com/v1",
+        )
+    )
+
+    assert isinstance(service, OpenAILLMService)