feat: configurable ElevenLabs base URL for Data Residency (#269)

Adds a `base_url` field to `ElevenlabsTTSConfiguration` so users on an
ElevenLabs Data Residency plan (EU, etc.) can point Dograh at the
regional endpoint instead of the hardcoded global one. Defaults to
`https://api.elevenlabs.io`, preserving existing behaviour. The
service factory rewrites the HTTP scheme to WSS when constructing the
WebSocket TTS service.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/services/configuration/registry.py

@@ -443,6 +443,14 @@ class ElevenlabsTTSConfiguration(BaseServiceConfiguration):
         default="eleven_flash_v2_5",
         json_schema_extra={"examples": ELEVENLABS_TTS_MODELS},
     )
+    base_url: str = Field(
+        default="https://api.elevenlabs.io",
+        description=(
+            "ElevenLabs API base URL. Override to use a Data Residency endpoint "
+            "(e.g. https://api.eu.residency.elevenlabs.io) for GDPR / HIPAA / "
+            "regional compliance."
+        ),
+    )
 
 
 OPENAI_TTS_MODELS = ["gpt-4o-mini-tts"]

api/services/pipecat/service_factory.py

@@ -247,9 +247,16 @@ def create_tts_service(user_config, audio_config: "AudioConfig"):
             voice_id = user_config.tts.voice.split(" - ")[1]
         except IndexError:
             voice_id = user_config.tts.voice
+        # ElevenLabs TTS uses WebSocket. Users configure base_url with an HTTP
+        # scheme (matching ElevenLabs documentation, e.g.
+        # https://api.eu.residency.elevenlabs.io); rewrite it to the WS scheme.
+        elevenlabs_url = user_config.tts.base_url.replace(
+            "https://", "wss://"
+        ).replace("http://", "ws://")
         return ElevenLabsTTSService(
             reconnect_on_error=False,
             api_key=user_config.tts.api_key,
+            url=elevenlabs_url,
             settings=ElevenLabsTTSSettings(
                 voice=voice_id,
                 model=user_config.tts.model,