feat: 0.1.1 — timeline scrubber, gallery virtualisation, folder reorder, QoL polish

Timeline:
- Add a right-edge scrubber (year labels + month dots) that jumps to any
  period; runs in the same direction as the scrolled content
- Load the full filtered set in Timeline view so the scrubber spans the whole
  library instead of just the first page

Gallery & UI:
- Virtualise the gallery grid
- Folder reordering in the sidebar (drag + persisted sort_order) and a themed
  dropdown component
- Subtle Light theme contrast fixes for toggles, secondary buttons and the
  update toast

Embedding workers now defer video jobs without a thumbnail at claim time and
requeue any previously-failed deferred jobs on startup, so videos no longer
churn through failed embeddings.

QoL polish across BackgroundTasks, DuplicateFinder, Lightbox and VideoPlayer.

src/components/UpdateToast.tsx

@@ -31,7 +31,7 @@ export function UpdateToast() {
               </p>
               <div className="mt-3 flex items-center gap-2">
                 <button
-                  className="rounded-md border border-emerald-400/35 bg-emerald-500/15 px-3 py-1.5 text-xs text-emerald-200 transition-colors hover:bg-emerald-500/25"
+                  className="rounded-md border border-emerald-400/35 bg-emerald-500/15 px-3 py-1.5 text-xs text-emerald-200 transition-colors hover:bg-emerald-500/25 light-theme:border-emerald-600/50 light-theme:bg-emerald-100 light-theme:text-emerald-700 light-theme:hover:bg-emerald-200"
                   onClick={() => void installUpdate()}
                 >
                   Install &amp; restart