Default to @ instead of $ on new configs when using a potentiometer

[tigert]

It would be good to use @ as the default value placeholder for new input configs for analog inputs that have a value field, as that's most likely what you want to use instead of $

Describe the solution you'd like When you add a mobiflight variable using a potentiometer, the default placeholder should be @.

Since MSFS events do not contain a "value" field, this issue is not that apparent (as presets then use @ when it makes sense) but many times you want to read the value into a MobiFlight Variable, and there the default placeholder definitely should be @ when setting up an analog input.

Additional context I am not sure if setting the input type is device-aware, so it might only have one template regardless if the input is for a button or analog input.