Move to Flutter 3.47, use the improvements that come with this (#64)

Reviewed-on: #64

lib/models/space.dart

@@ -3,16 +3,15 @@ import "package:flutter/widgets.dart";
 import "package:freezed_annotation/freezed_annotation.dart";
 import "package:nexus/models/room.dart";
 import "package:nexus/models/subspace.dart";
+
 part "space.freezed.dart";
 
 @freezed
-abstract class Space with _$Space {
-  const factory Space({
-    required String id,
-    required String title,
-    IconData? icon,
-    Room? room,
-    required IList<Room> children,
-    required IList<Subspace> subSpaces,
-  }) = _Space;
-}
+class const Space({
+  required final String id,
+  required final String title,
+  final IconData? icon,
+  final Room? room,
+  required final IList<Room> children,
+  required final IList<Subspace> subSpaces,
+}) with _$Space;