✨(backend) add metadata collection of VAD, connection and chat events

Introduce MetadataCollector and MetadataCollectorService classes to
centralize the collection and storage of user connections, VAD events,
and chat messages. This creates a structured foundation for future speaker
assignment logic based on voice activity detection. Add tests for this new
feature.

src/backend/core/tests/rooms/test_api_rooms_start_recording.py

@@ -277,6 +277,7 @@ def test_start_recording_options_transcribe_valid_true(
 ):
     """Should accept transcribe with any valid pydantic true values."""
     settings.RECORDING_ENABLE = True
+    settings.METADATA_COLLECTOR_ENABLED = False
     room = RoomFactory()
     user = UserFactory()
     room.accesses.create(user=user, role="owner")
@@ -487,6 +488,93 @@ def test_start_recording_options_original_mode_omitted(
     assert recording.options == {}
 
 
+def test_start_recording_calls_metadata_collector_start(
+    settings, mock_worker_service_factory, mock_worker_manager
+):
+    """Should call MetadataCollectorService.start when conditions are met."""
+    settings.RECORDING_ENABLE = True
+    settings.METADATA_COLLECTOR_ENABLED = True
+
+    room = RoomFactory()
+    user = UserFactory()
+    room.accesses.create(user=user, role="owner")
+
+    client = APIClient()
+    client.force_login(user)
+
+    with mock.patch(
+        "core.api.viewsets.MetadataCollectorService"
+    ) as mock_collector_class:
+        mock_collector = mock.Mock()
+        mock_collector_class.return_value = mock_collector
+
+        response = client.post(
+            f"/api/v1.0/rooms/{room.id}/start-recording/",
+            {
+                "mode": "screen_recording",
+                "options": {"transcribe": True, "collect_metadata": True},
+            },
+            format="json",
+        )
+
+    assert response.status_code == 201
+
+    recording = Recording.objects.get(room=room)
+    mock_collector.start.assert_called_once_with(recording)
+
+
+@pytest.mark.parametrize(
+    "metadata_enabled,options",
+    [
+        # Metadata collector disabled, regardless of transcribe option
+        (False, {"transcribe": True}),
+        (False, {"transcribe": False}),
+        (False, None),
+        # Metadata collector enabled, but transcribe is False or missing
+        (True, {"transcribe": False}),
+        (True, None),
+        # Metadata collector enabled, transcribe True, but collect_metadata explicitly False
+        (True, {"transcribe": True, "collect_metadata": False}),
+    ],
+)
+def test_start_recording_does_not_call_metadata_collector_start_when_conditions_not_met(
+    settings,
+    mock_worker_service_factory,
+    mock_worker_manager,
+    metadata_enabled,
+    options,
+):
+    """Should not call MetadataCollectorService.start when conditions are not met."""
+    settings.RECORDING_ENABLE = True
+    settings.METADATA_COLLECTOR_ENABLED = metadata_enabled
+
+    room = RoomFactory()
+    user = UserFactory()
+    room.accesses.create(user=user, role="owner")
+
+    client = APIClient()
+    client.force_login(user)
+
+    payload = {"mode": "screen_recording"}
+    if options is not None:
+        payload["options"] = options
+
+    with mock.patch(
+        "core.api.viewsets.MetadataCollectorService"
+    ) as mock_collector_class:
+        mock_collector = mock.Mock()
+        mock_collector_class.return_value = mock_collector
+
+        response = client.post(
+            f"/api/v1.0/rooms/{room.id}/start-recording/",
+            payload,
+            format="json",
+        )
+
+    assert response.status_code == 201
+    mock_collector.start.assert_not_called()
+
+
 @pytest.mark.parametrize("value", ["invalid_mode", "foo", 123, "SCREEN_RECORDING"])
 def test_start_recording_options_original_mode_invalid(settings, value):
     """Should reject invalid recording mode values for original_mode."""

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

@@ -269,6 +269,63 @@ def test_handle_egress_ended_recording_not_limit_reached(
     assert recording.status == "stopped"
 
 
+@mock.patch("core.services.livekit_events.MetadataCollectorService")
+@mock.patch("core.utils.update_room_metadata")
+def test_handle_egress_ended_calls_metadata_collector_stop_when_conditions_are_met(
+    mock_update_room_metadata, mock_collector_class, service, settings
+):
+    """Should call MetadataCollectorService.stop when it exists."""
+    settings.METADATA_COLLECTOR_ENABLED = True
+
+    recording = RecordingFactory(
+        worker_id="worker-1",
+        status="active",
+        options={"metadata_collector_dispatch_id": "dispatch-123"},
+    )
+    mock_data = mock.MagicMock()
+    mock_data.egress_info.egress_id = recording.worker_id
+    mock_data.egress_info.status = EgressStatus.EGRESS_COMPLETE
+
+    mock_collector = mock.Mock()
+    mock_collector_class.return_value = mock_collector
+
+    service._handle_egress_ended(mock_data)
+
+    mock_collector.stop.assert_called_once_with(recording)
+
+
+@pytest.mark.parametrize(
+    "metadata_enabled,options",
+    [
+        (True, {}),
+        (False, {}),
+    ],
+)
+@mock.patch("core.services.livekit_events.MetadataCollectorService")
+@mock.patch("core.utils.update_room_metadata")
+def test_handle_egress_ended_does_not_call_metadata_collector_stop_when_conditions_not_met(
+    _, mock_collector_class, metadata_enabled, options, service, settings
+):  # pylint: disable=too-many-arguments,too-many-positional-arguments
+    """Should not call MetadataCollectorService.stop when it does not exist."""
+    settings.METADATA_COLLECTOR_ENABLED = metadata_enabled
+
+    recording = RecordingFactory(
+        worker_id="worker-1",
+        status="active",
+        options=options,
+    )
+    mock_data = mock.MagicMock()
+    mock_data.egress_info.egress_id = recording.worker_id
+    mock_data.egress_info.status = EgressStatus.EGRESS_COMPLETE
+
+    mock_collector = mock.Mock()
+    mock_collector_class.return_value = mock_collector
+
+    service._handle_egress_ended(mock_data)
+
+    mock_collector.stop.assert_not_called()
+
+
 @mock.patch.object(LobbyService, "clear_room_cache")
 @mock.patch.object(TelephonyService, "delete_dispatch_rule")
 def test_handle_room_finished_clears_cache_and_deletes_dispatch_rule(