[ flox1an/nostube ] fix(zaps): update cached zap amount when switching videos
Changed useEventZaps to use useMemo instead of useState for the cached
value, so it recalculates when eventId changes. Previously the cached
value was only set once on mount, causing stale zap amounts to display
when navigating between videos.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>