🐛(backend) ensure SIP dispatch rule instead of creating it

The roomkit can now create a SIP dispatch rule before the LiveKit
webhook that used to trigger this creation is fired. In practice,
when the roomkit connects to the room, it also triggers the
webhook, leading to a duplicated dispatch rule.

Switch from "create dispatch rule" to "ensure dispatch rule exists"
semantics, so subsequent calls are idempotent and no duplicate rule
is created.

src/backend/core/services/livekit_events.py

@@ -247,7 +247,7 @@ class LiveKitEventsService:
 
         if settings.ROOM_TELEPHONY_ENABLED or settings.ROOMKIT_ENABLED:
             try:
-                self.sip_management.create_dispatch_rule(room)
+                self.sip_management.ensure_dispatch_rule(room)
             except SIPException as e:
                 raise ActionFailedError(
                     f"Failed to create sip dispatch rule for room {room_id}"

src/backend/core/tests/services/test_livekit_events.py

@@ -21,7 +21,10 @@ from core.services.livekit_events import (
 )
 from core.services.lobby import LobbyService
 from core.services.room_management import RoomManagementException
-from core.services.sip_management import SIPException, SIPManagement
+from core.services.sip_management import (
+    SIPException,
+    SIPManagement,
+)
 from core.utils import NotificationError
 
 pytestmark = pytest.mark.django_db
@@ -581,11 +584,11 @@ def test_handle_room_finished_raises_error_for_invalid_room_name(service):
         service._handle_room_finished(mock_data)
 
 
-@mock.patch.object(SIPManagement, "create_dispatch_rule")
+@mock.patch.object(SIPManagement, "ensure_dispatch_rule")
 def test_handle_room_started_creates_dispatch_rule_successfully(
-    mock_create_dispatch_rule, service, settings
+    mock_ensure_dispatch_rule, service, settings
 ):
-    """Should create SIP dispatch rule when room starts successfully."""
+    """Should ensure the SIP dispatch rule exists when room starts successfully."""
     settings.ROOM_TELEPHONY_ENABLED = True
     room = RoomFactory()
     mock_data = mock.MagicMock()
@@ -593,14 +596,14 @@ def test_handle_room_started_creates_dispatch_rule_successfully(
 
     service._handle_room_started(mock_data)
 
-    mock_create_dispatch_rule.assert_called_once_with(room)
+    mock_ensure_dispatch_rule.assert_called_once_with(room)
 
 
-@mock.patch.object(SIPManagement, "create_dispatch_rule")
+@mock.patch.object(SIPManagement, "ensure_dispatch_rule")
 def test_handle_room_started_creates_dispatch_rule_when_only_roomkit_enabled(
-    mock_create_dispatch_rule, service, settings
+    mock_ensure_dispatch_rule, service, settings
 ):
-    """Should create dispatch rule when only roomkit is enabled during room start."""
+    """Should ensure the dispatch rule exists when only roomkit is enabled during room start."""
     settings.ROOM_TELEPHONY_ENABLED = False
     settings.ROOMKIT_ENABLED = True
     room = RoomFactory()
@@ -609,14 +612,50 @@ def test_handle_room_started_creates_dispatch_rule_when_only_roomkit_enabled(
 
     service._handle_room_started(mock_data)
 
-    mock_create_dispatch_rule.assert_called_once_with(room)
+    mock_ensure_dispatch_rule.assert_called_once_with(room)
 
 
-@mock.patch.object(SIPManagement, "create_dispatch_rule")
-def test_handle_room_started_skips_dispatch_rule_when_telephony_disabled(
-    mock_create_dispatch_rule, service, settings
+@mock.patch.object(SIPManagement, "ensure_dispatch_rule", return_value=False)
+def test_handle_room_started_ignores_existing_dispatch_rule(
+    mock_ensure_dispatch_rule, service, settings
 ):
-    """Should skip creating SIP dispatch rule when telephony is disabled during room start."""
+    """Should proceed silently when the dispatch rule already exists when room starts."""
+    settings.ROOM_TELEPHONY_ENABLED = True
+    room = RoomFactory()
+    mock_data = mock.MagicMock()
+    mock_data.room.name = str(room.id)
+
+    # ensure_dispatch_rule reports the rule as pre-existing: nothing to raise
+    service._handle_room_started(mock_data)
+
+    mock_ensure_dispatch_rule.assert_called_once_with(room)
+
+
+@mock.patch.object(
+    SIPManagement,
+    "ensure_dispatch_rule",
+    side_effect=SIPException("Test error"),
+)
+def test_handle_room_started_raises_error_when_dispatch_rule_creation_fails(
+    mock_ensure_dispatch_rule, service, settings
+):
+    """Should raise ActionFailedError when ensuring the dispatch rule fails when room starts."""
+    settings.ROOM_TELEPHONY_ENABLED = True
+    room = RoomFactory()
+    mock_data = mock.MagicMock()
+    mock_data.room.name = str(room.id)
+
+    expected_error = f"Failed to create sip dispatch rule for room {room.id}"
+
+    with pytest.raises(ActionFailedError, match=expected_error):
+        service._handle_room_started(mock_data)
+
+
+@mock.patch.object(SIPManagement, "ensure_dispatch_rule")
+def test_handle_room_started_skips_dispatch_rule_when_telephony_disabled(
+    mock_ensure_dispatch_rule, service, settings
+):
+    """Should skip ensuring the SIP dispatch rule when telephony is disabled during room start."""
     settings.ROOM_TELEPHONY_ENABLED = False
     settings.ROOMKIT_ENABLED = False
     room = RoomFactory()
@@ -625,7 +664,7 @@ def test_handle_room_started_skips_dispatch_rule_when_telephony_disabled(
 
     service._handle_room_started(mock_data)
 
-    mock_create_dispatch_rule.assert_not_called()
+    mock_ensure_dispatch_rule.assert_not_called()
 
 
 def test_handle_room_started_raises_error_for_invalid_room_name(service):