feat(library): reindex button, live grid, archive-reappear fix, bigger carets

- Add one-click "reindex new files" button to the Library sidebar header
  (RefreshCw, calls startIndex rescan:false), spins + disables while active.
- Refresh the photos grid from the indexer WS stream (throttled during the
  scan + once on completion) so newly indexed files appear live.
- Fix archived photos flashing back into the grid when archiving others:
  drop the per-action settle-driven clearRemoved and reconcile removedIds
  against the actual cache instead (clears an id only once it's gone from
  the deduped pages). Covers archive, delete, and bulk-bar removals.
- Replace the tiny Unicode caret triangles with a 16px Lucide ChevronRight
  that rotates 90deg on expand, across folder tree rows, root, Tags, Review.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/src/routes/+page.svelte

@@ -37,7 +37,7 @@
     setFocused,
     setOrder,
   } from "$lib/stores/selection.svelte";
-  import { removedIds } from "$lib/stores/bulkAction.svelte";
+  import { removedIds, clearRemoved } from "$lib/stores/bulkAction.svelte";
   import {
     openPreview,
     setRightSidebarWidth,
@@ -283,6 +283,20 @@
   }
   const pageCount = $derived(photosQuery.data?.pages.length ?? 0);
 
+  // Reconcile the optimistic-removal overlay against the actual cache.
+  // `removedIds` hides a tile while its photo is still present in a loaded
+  // page; we drop an id from the set only once it has genuinely left the
+  // freshly-deduped cache (i.e. every page that held it has refetched
+  // without it). Driving the clear from the data — rather than from each
+  // archive action's invalidation promise — removes the race where settling
+  // one action's refetch un-hid a photo that other, still-stale pages
+  // continued to carry, making archived tiles flash back into the grid.
+  $effect(() => {
+    const present = new Set(dedupedAll.map((p) => p.UID));
+    const gone = [...removedIds].filter((id) => !present.has(id));
+    if (gone.length) clearRemoved(gone);
+  });
+
   $effect(() => {
     setOrder(photos.map((p) => p.UID));
   });