Memories view now supports the same keyboard shortcuts, heap membership,
and optimistic cache updates as the Timeline. Arrow/Ctrl+A/Escape nav is
extracted into a shared useGridKeyNav hook so both views stay in lockstep.
Duplicates view is virtualised with @tanstack/react-virtual and has
stabilised PhotoThumbnail props so React.memo actually elides work when
scrolling or toggling selection.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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