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.

Start in frontend/src/common/buttons/BoostButton.jsx at the referenced lines, since that is where the workaround is currently implemented. Then inspect the components/hooks that pass data into BoostButton to find an existing authoritative way the boosted state is represented for the current pod user. Run the relevant frontend button/component tests (or add one if one exists for this area) and confirm the button correctly indicates and behaves for already-boosted activities without the hacky path.

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