Include fields without metadata in _get_features()

Fields like movement_direction (which has init=False but no metadata)
were being excluded from available_properties, causing validation
errors in the HA integration options flow.

Author: chkuendig

src/pyftms/serializer/model.py

@@ -183,7 +183,7 @@ def _get_cls_features(cls):
             for field in dc.fields(cls):
                 meta, tp = cast(ModelMeta, field.metadata), field.type
 
-                if not meta or field.name == "code":
+                if field.name == "code":
                     continue
 
                 if get_origin(tp) in (Optional, Union, UnionType):