Find a non hacky way to determine if an as:object has already been boosted by a pod's user

# Context
This is a followup task to keep track of the workaround that was implemented to determine if a given pod user as already boosted a given activity.

see #50 and particularly [this comment](https://github.com/activitypods/mastopod/issues/50#issuecomment-2717666433) that highlights the hacky workaround that has been implemented.
https://github.com/activitypods/mastopod/blob/f04ecb570557614c6010c920a7cbfc606c7f7f21/frontend/src/common/buttons/BoostButton.jsx#L14-L15

# TODO

Find a non hacky yet performant way to handle this situation.