feat: add Azure AI multi-provider support (TTS, STT, Embeddings, Realtime)

Enables Azure AI services across all model layers so users with Azure
credits can consolidate billing on a single provider.

- Voice (TTS): AzureSpeechTTSConfiguration via azure_speech provider
- Transcriber (STT): AzureSpeechSTTConfiguration via azure_speech provider
- Embedding: AzureOpenAIEmbeddingsConfiguration via azure provider
- Realtime: AzureRealtimeLLMConfiguration via azure_realtime provider

New files:
- api/services/pipecat/realtime/azure_realtime.py
- api/services/gen_ai/embedding/azure_openai_service.py
- api/tests/test_azure_speech_service_factory.py

The UI picks up all four providers automatically from the schema —
no frontend changes required.

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

api/services/workflow/pipecat_engine.py

@@ -73,6 +73,9 @@ class PipecatEngine:
         embeddings_api_key: Optional[str] = None,
         embeddings_model: Optional[str] = None,
         embeddings_base_url: Optional[str] = None,
+        embeddings_provider: Optional[str] = None,
+        embeddings_endpoint: Optional[str] = None,
+        embeddings_api_version: Optional[str] = None,
         has_recordings: bool = False,
         context_compaction_enabled: bool = False,
     ):
@@ -126,6 +129,9 @@ class PipecatEngine:
         self._embeddings_api_key: Optional[str] = embeddings_api_key
         self._embeddings_model: Optional[str] = embeddings_model
         self._embeddings_base_url: Optional[str] = embeddings_base_url
+        self._embeddings_provider: Optional[str] = embeddings_provider
+        self._embeddings_endpoint: Optional[str] = embeddings_endpoint
+        self._embeddings_api_version: Optional[str] = embeddings_api_version
 
         # Audio configuration (set via set_audio_config from _run_pipeline)
         self._audio_config = None
@@ -373,6 +379,9 @@ class PipecatEngine:
                     embeddings_api_key=self._embeddings_api_key,
                     embeddings_model=self._embeddings_model,
                     embeddings_base_url=self._embeddings_base_url,
+                    embeddings_provider=self._embeddings_provider,
+                    embeddings_endpoint=self._embeddings_endpoint,
+                    embeddings_api_version=self._embeddings_api_version,
                     tracing_context=self._get_otel_context(),
                 )