fix: Allow firmware version as an optional field (#670)

* fix: Allow firmware version as an optional field

This field may not be returned by the API, in particular when the device is offline.

```
2025-12-14 18:09:25.550 ERROR (MainThread) [roborock.data.containers] Failed to convert devices with value [{'duid': 'yyyyyy', 'name': 'S6 Pure', 'localKey': 'xxxxxx', 'productId': 'zzzzzz', 'activeTime': NNNNNNN, 'timeZoneId': 'Europe/Moscow', 'iconUrl': '', 'share': False, 'online': False, 'pv': '1.0', 'tuyaMigrated': False, 'extra': '{}', 'deviceStatus': {}, 'silentOtaSwitch': False, 'f': False}] to type list[roborock.data.containers.HomeDataDevice]
Traceback (most recent call last):
  File "/usr/local/lib/python3.13/site-packages/roborock/data/containers.py", line 122, in from_dict
    result[key] = RoborockBase._convert_to_class_obj(field_type, value)
                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/roborock/data/containers.py", line 73, in _convert_to_class_obj
    return [RoborockBase._convert_to_class_obj(sub_type, obj) for obj in value]
            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/roborock/data/containers.py", line 81, in _convert_to_class_obj
    return class_type.from_dict(value)
           ~~~~~~~~~~~~~~~~~~~~^^^^^^^
  File "/usr/local/lib/python3.13/site-packages/roborock/data/containers.py", line 127, in from_dict
    return cls(**result)
TypeError: HomeDataDevice.__init__() missing 1 required positional argument: 'fv'
```

* chore: add test for example offline device

Author: allenporter

roborock/data/containers.py

@@ -238,8 +238,8 @@ class HomeDataDevice(RoborockBase):
     duid: str
     name: str
     local_key: str
-    fv: str
     product_id: str
+    fv: str | None = None
     attribute: Any | None = None
     active_time: int | None = None
     runtime_env: Any | None = None