fix: number pool initialization in multi telephony setup

If there are multiple telephony configurations, the form number should be initialized from the campaigns given telephonic configuration rather than the organization default telephonic configuration.

api/routes/telephony.py

@@ -55,6 +55,9 @@ class InitiateCallRequest(BaseModel):
     # Optional explicit telephony config to use for the test call. If omitted,
     # falls back to the user's per-user default (when set), then the org default.
     telephony_configuration_id: int | None = None
+    # Optional caller-ID phone number to dial out from. Must belong to the
+    # resolved telephony configuration; otherwise the provider picks one.
+    from_phone_number_id: int | None = None
 
 
 @router.post(
@@ -173,11 +176,29 @@ async def initiate_call(
 
     keywords = {"workflow_id": request.workflow_id, "user_id": user.id}
 
+    # Resolve optional caller-ID. The config has already been validated against
+    # the user's organization, so filtering by config_id is sufficient for
+    # tenant isolation.
+    from_number: str | None = None
+    if request.from_phone_number_id is not None:
+        if telephony_configuration_id is None:
+            raise HTTPException(
+                status_code=400,
+                detail="from_phone_number_id_requires_telephony_configuration",
+            )
+        phone_row = await db_client.get_phone_number_for_config(
+            request.from_phone_number_id, telephony_configuration_id
+        )
+        if not phone_row or not phone_row.is_active:
+            raise HTTPException(status_code=400, detail="from_phone_number_not_found")
+        from_number = phone_row.address_normalized
+
     # Initiate call via provider
     result = await provider.initiate_call(
         to_number=phone_number,
         webhook_url=webhook_url,
         workflow_run_id=workflow_run_id,
+        from_number=from_number,
         **keywords,
     )