The sidebar tag list wasn't updating when users created new memos with tags
or modified existing memo tags. This was because useFilteredMemoStats hook
only refetched when filter/state/orderBy changed.

Now the hook observes memoStore.state.stateId, which changes whenever memos
are created, updated, or deleted. This triggers automatic refetch and the
sidebar updates immediately with the latest tag counts.

Fixes tag refresh issue in sidebar