#182 shipped hydrateAuthImages() loading every thumbnail immediately, which
regressed the content-library grid from lazy to eager (a fetch per thumbnail on
render) and left the IntersectionObserver as dead code.
Restore lazy-by-default (observe-only) so large grids only fetch thumbnails as
they scroll into view, and add an { eager: true } opt-in for the transient
pickers where every item is on screen and immediate load reads better: the
device assign-content modal, the playlist add-item modal, and the widget
content picker. Grids and inline lists (content library, playlist items, device
playlist tab, directory logo/background) use the lazy default.
Behavior for those pickers is unchanged; only the large grids revert to the
lazy loading they had before #182.
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>