perf(frontend): invalidate duplicate-scan cache concurrently and safely

Cache invalidation across affected folders after a bulk delete ran
sequentially through awaited invoke calls, duplicated between
gallerySlice and duplicateSlice. Extract a shared
invalidateDuplicateScanCaches helper that batches the calls with
Promise.allSettled, logging failures instead of throwing — a
best-effort cache refresh should never turn an already-successful
delete into a rejected promise for the caller.

src/store/duplicateSlice.ts

@@ -1,6 +1,7 @@
 import { invoke } from '@tauri-apps/api/core'
 import type { StateCreator } from 'zustand'
 import { notifyTaskComplete } from '../notifications'
+import { invalidateDuplicateScanCaches } from './helpers'
 import type { GalleryStore } from './index'
 import type { DuplicateGroup, DuplicateScanProgress, DuplicateScanResult } from './types'
 
@@ -146,10 +147,7 @@ export const createDuplicateSlice: StateCreator<GalleryStore, [], [], DuplicateS
         .filter((img) => succeededSet.has(img.id))
         .map((img) => img.folder_id)
     )
-    await invoke('invalidate_duplicate_scan_cache', { folderId: null }) // global
-    for (const folderId of affectedFolderIds) {
-      await invoke('invalidate_duplicate_scan_cache', { folderId })
-    }
+    await invalidateDuplicateScanCaches(affectedFolderIds)
     return succeededIds.length
   },
 })

src/store/gallerySlice.ts

@@ -3,6 +3,7 @@ import type { StateCreator } from 'zustand'
 import {
   PAGE_SIZE,
   TIMELINE_PAGE_SIZE,
+  invalidateDuplicateScanCaches,
   isCurrentGalleryRequest,
   isDerivedCollectionTitle,
   mergeImages,
@@ -608,10 +609,7 @@ export const createGallerySlice: StateCreator<GalleryStore, [], [], GallerySlice
     }))
     // The DB cascade already removed these from album_images; refresh counts/covers.
     void get().loadAlbums()
-    await invoke('invalidate_duplicate_scan_cache', { folderId: null })
-    for (const folderId of affectedFolderIds) {
-      await invoke('invalidate_duplicate_scan_cache', { folderId })
-    }
+    await invalidateDuplicateScanCaches(affectedFolderIds)
     return succeededIds.length
   },
 })

src/store/helpers.ts

@@ -1,3 +1,4 @@
+import { invoke } from '@tauri-apps/api/core'
 import type {
   ImageRecord,
   MediaFilter,
@@ -268,6 +269,26 @@ export function scopeHasTaggingPending(
   return (progressByFolder[folderId]?.tagging_pending ?? 0) > 0
 }
 
+// Invalidates the persisted duplicate-scan cache for every scope affected by a
+// deletion: the global "all" cache (always, since a folder-scoped deletion
+// still makes the global result stale) and each folder that contained a
+// deleted image. This is a best-effort background refresh — a failure here
+// must not turn an already-successful delete into a rejected promise for the
+// caller, so failures are logged rather than thrown.
+export async function invalidateDuplicateScanCaches(affectedFolderIds: Set<number>): Promise<void> {
+  const results = await Promise.allSettled([
+    invoke('invalidate_duplicate_scan_cache', { folderId: null }),
+    ...[...affectedFolderIds].map((folderId) =>
+      invoke('invalidate_duplicate_scan_cache', { folderId })
+    ),
+  ])
+  for (const result of results) {
+    if (result.status === 'rejected') {
+      console.error('Failed to invalidate duplicate-scan cache:', result.reason)
+    }
+  }
+}
+
 export function taggingProgressAffectsScope(
   progressFolderId: number,
   scopeFolderId: number | null