Each /state poll fired ~10 getAppSetting reads to resolve the watermark/fit;
a leaked link x N tabs amplified that linearly (review concern 2). Add a
5s-TTL cached bundle (utils/slideshowGlobals) for the global slideshow_* +
branding-logo settings, invalidated on PUT /admin/settings/slideshow so admin
live-edit stays instant. slideshowSettings now does ~2 reads per poll (event
row + photo count) on a cache hit. Also documents the frontend
optimistic-default nit.