activeSyncCount/isSyncing() in useFeeds.js already refcounted both boot
reload (fetchData) and manual sync() but wasn't reactive. Make it a ref
+ computed and expose it so AppNav can render a small spinner next to
the feed filter whenever a sync is in flight.
The spinner sits outside the filter's own v-if so it also shows during
a manual sync from pages other than /feeds, and its box is always
reserved (visibility toggle, not v-if) so the one-time --app-nav-height
measurement stays correct.
mathias