feat: revamp sensor add flow

lib/data/repositories/phoenix_sensor_repository.dart

@@ -1,11 +1,20 @@
 import '../../domain/models/sensor.dart';
+import '../sources/localiser/realtime_data_client.dart';
 import '../sources/localiser/sensor_client.dart';
 import 'sensor_repository.dart';
 
 class PhoenixSensorRepository implements SensorRepository {
-  const PhoenixSensorRepository({required this.client});
+  const PhoenixSensorRepository({
+    required this.client,
+    required this.realtime,
+  });
 
   final SensorClient client;
+  final RealtimeDataClient realtime;
+
+  @override
+  Future<Sensor> createSensor(String sensorId, {String? name}) async =>
+      Sensor.fromJson(await client.createSensor(sensorId, name: name));
 
   @override
   Future<List<Sensor>> getSensors() async {
@@ -35,11 +44,16 @@ class PhoenixSensorRepository implements SensorRepository {
 
   @override
   Future<Sensor> placeSensor(int id,
-      {required int roomId, required double x, required double y}) async =>
+          {required int roomId, required double x, required double y}) async =>
       Sensor.fromJson(
           await client.placeSensor(id, {'room_id': roomId, 'x': x, 'y': y}));
 
   @override
   Future<Sensor> unplaceSensor(int id) async =>
       Sensor.fromJson(await client.unplaceSensor(id));
+
+  @override
+  Stream<Map<String, dynamic>> sensorEvents() => realtime
+      .channelMessages('sensors')
+      .map((m) => {'event': m.event, ...m.payload});
 }

lib/data/repositories/sensor_repository.dart

@@ -1,6 +1,7 @@
 import '../../domain/models/sensor.dart';
 
 abstract class SensorRepository {
+  Future<Sensor> createSensor(String sensorId, {String? name});
   Future<List<Sensor>> getSensors();
   Future<List<Sensor>> getUnplacedSensors();
   Future<Sensor> getSensor(int id);
@@ -9,4 +10,8 @@ abstract class SensorRepository {
   Future<Sensor> placeSensor(int id,
       {required int roomId, required double x, required double y});
   Future<Sensor> unplaceSensor(int id);
+
+  /// Stream of raw SensorsChannel messages. Each map contains an `event` key
+  /// (`sensor_announced` or `sensor_enrollment_timeout`) plus the payload.
+  Stream<Map<String, dynamic>> sensorEvents();
 }