Temperature range does not work in Fahrenheit

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Checklist

• I have filled out the template to the best of my ability.
• This only contains 1 feature request (if you have multiple feature requests, open one feature request for each feature request).
• This issue is not a duplicate feature request of previous feature requests.

Is your feature request related to a problem? Please describe.

The temperature unit of the temperature range is locked to Celsius. This is because if the temperature units of home assistant are set to Fahrenheit, the temperature range 0°C - 4°C is converted to 32°F - 39°F. It should be 0°F - 7.2°F.

The lock is enforced by setting device_class to None:

HomeAssistant-OptiSpark/custom_components/optispark/number.py

Lines 58 to 71 in 73a252b

	OptisparkNumber(
	coordinator=coordinator,
	entity_description=NumberEntityDescription(
	key="temperature_range",
	name="Temperature Range",
	icon="mdi:gauge"),
	native_value=3,
	native_step=0.5,
	native_max_value=4,
	native_min_value=0,
	lambda_parameter=const.LAMBDA_TEMP_RANGE,
	device_class=None,
	native_unit_of_measurement='°C'
	)

Describe the solution you'd like

When home assistant temperature units are set to Fahrenheit, the temperature range should be converted to a sensible range in Fahrenheit, such as 0°F - 7°F with a step size of 1°F.

Describe alternatives you've considered

Additional context