perf: batch artist image loading for library grid view

Replace per-artist sequential GetArtistMBID + GetArtistImageURL
calls (2 Wails round-trips × N artists) with a single batch
GetArtistImages(names[]) call that:

1. Resolves all names → MBIDs via AllArtistMBIDs() (one DB query)
2. Checks disk cache for each MBID via GetCachedImage (no network)
3. Returns map[name]→dataURL in one Wails bridge round-trip

Only returns already-cached images from the disk cache populated
by the index build. No network fetches triggered — artists whose
images haven't been cached yet keep the initial letter fallback
until the index build resolves them in the background.

Result: all cached artist images appear simultaneously on first
render instead of loading one-by-one over several seconds.

backend/explore/artistimage.go

@@ -76,6 +76,16 @@ func NewArtistImageProvider(
 	}
 }
 
+// GetCachedImage returns a base64 data URL from the disk cache
+// only — no network fetches.  Returns "" if not cached.
+func (p *ArtistImageProvider) GetCachedImage(artistMBID string) string {
+	if artistMBID == "" || p.imageDir == "" {
+		return ""
+	}
+
+	return p.readDiskCache(artistMBID)
+}
+
 // GetArtistImage returns a base64 data URL for the artist's photo.
 // Checks disk cache first, then resolves via MB/Wikidata and fetches
 // the image from Wikimedia Commons.  Returns "" if no image.

backend/explore/explore.go

@@ -233,6 +233,32 @@ func (e *Service) GetArtistMBID(artistName string) string {
 	return e.libMBID.GetArtistMBID(artistName)
 }
 
+// GetArtistImages resolves artist images for multiple artists by
+// name in one call.  Returns a map of artist name → base64 data
+// URL.  Only artists with cached images are returned — no network
+// fetches are triggered (use GetArtistImageURL for on-demand fetch).
+func (e *Service) GetArtistImages(names []string) map[string]string {
+	result := make(map[string]string, len(names))
+
+	// Batch resolve all names → MBIDs from the library DB.
+	allMBIDs := e.libMBID.AllArtistMBIDs()
+
+	for _, name := range names {
+		mbid, ok := allMBIDs[name]
+		if !ok || mbid == "" {
+			continue
+		}
+
+		// Only return already-cached images — don't trigger fetches.
+		img := e.artistImg.GetCachedImage(mbid)
+		if img != "" {
+			result[name] = img
+		}
+	}
+
+	return result
+}
+
 // Search concurrently queries MusicBrainz for artists, release
 // groups, and recordings matching the query, then boosts results
 // using ListenBrainz popularity data.  The final score blends

frontend/src/components/artists-view/artists-view.ts

@@ -16,7 +16,7 @@ import {
     GetAlbumsByArtistByLibrary,
     GetAlbumTracksByLibrary,
 } from '@go/library/Library';
-import { GetArtistImageURL, GetArtistMBID } from '@go/explore/Service';
+import { GetArtistImageURL, GetArtistMBID, GetArtistImages } from '@go/explore/Service';
 import { library } from '@go/models';
 import { LibraryController } from '@store/controllers/library-controller';
 import { SearchController } from '@store/controllers/search-controller';
@@ -439,6 +439,8 @@ export class ArtistsView
         ) {
             this.lastArtistsRef = cached;
             this.loadArtists();
+            this.imagesBatchLoaded = false;
+            void this.loadArtistImagesBatch();
         }
     }
 
@@ -454,6 +456,9 @@ export class ArtistsView
                 await this.libraryCtrl.getArtists();
 
             this.artists = artists ?? [];
+
+            // Batch load artist images after artists are loaded.
+            void this.loadArtistImagesBatch();
         } catch (error) {
             console.error(
                 'Error loading artists:',
@@ -988,11 +993,6 @@ export class ArtistsView
     private renderArtistAvatar(name: string) {
         const imageURL = this.artistImageCache.get(name);
 
-        // Kick off async image load if not cached.
-        if (!this.artistImageCache.has(name)) {
-            this.loadArtistImage(name);
-        }
-
         if (imageURL) {
             return html`<img
                 class="avatar-image"
@@ -1006,9 +1006,45 @@ export class ArtistsView
         </span>`;
     }
 
+    private imagesBatchLoaded = false;
+
     /**
-     * Load artist image for a single artist. Resolves MBID by name,
+     * Batch load all artist images in one Wails call.
-     * then fetches the cached image. Sequential to avoid rate limit.
+     * Only returns already-cached images (from the disk cache
+     * populated by the index build). Uncached artists fall back
+     * to the initial letter.
+     */
+    private async loadArtistImagesBatch() {
+        if (this.imagesBatchLoaded) return;
+
+        this.imagesBatchLoaded = true;
+
+        const artists = this.libraryCtrl.cachedArtists;
+
+        if (!artists || artists.length === 0) return;
+
+        const names = artists.map((a) => a.Name);
+
+        try {
+            const images = await GetArtistImages(names);
+
+            if (images && Object.keys(images).length > 0) {
+                for (const [name, url] of Object.entries(images)) {
+                    if (url) {
+                        this.artistImageCache.set(name, url);
+                    }
+                }
+
+                this.requestUpdate();
+            }
+        } catch {
+            // Non-critical.
+        }
+    }
+
+    /**
+     * Load artist image for a single artist on-demand (fallback
+     * for artists not resolved by the batch call).
      */
     private loadArtistImage(name: string) {
         if (this.artistImageCache.has(name) || this.artistImageLoading.has(name)) {

frontend/wailsjs/go/explore/Service.d.ts

@@ -7,16 +7,22 @@ export function BrowseReleaseGroups(arg1:string):Promise<Array<explore.MBRelease
 
 export function BrowseReleases(arg1:string):Promise<Array<explore.MBRelease>>;
 
+export function CheckLibraryMBIDs(arg1:Array<string>):Promise<Record<string, string>>;
+
 export function CoverArtGroupURL(arg1:string):Promise<string>;
 
 export function CoverArtURL(arg1:string):Promise<string>;
 
 export function GetArtistImageURL(arg1:string):Promise<string>;
 
+export function GetArtistMBID(arg1:string):Promise<string>;
+
 export function GetThumbnail(arg1:string,arg2:string,arg3:string):Promise<string>;
 
 export function GetThumbnails(arg1:Array<explore.ThumbnailRequest>):Promise<Record<string, string>>;
 
+export function InvalidateIndexDiscographies():Promise<void>;
+
 export function LookupArtist(arg1:string):Promise<explore.MBArtist>;
 
 export function LookupReleaseGroup(arg1:string):Promise<explore.MBReleaseGroup>;
@@ -33,8 +39,10 @@ export function SetContext(arg1:context.Context):Promise<void>;
 
 export function SimilarArtists(arg1:string):Promise<Array<explore.LBSimilarArtist>>;
 
+export function StartIndexBuild():Promise<void>;
+
+export function StopIndexBuild():Promise<void>;
+
 export function TopRecordingsForArtist(arg1:string):Promise<Array<explore.LBTopRecording>>;
 
-export function CheckLibraryMBIDs(arg1:string[]):Promise<Record<string, string>>;
+export function GetArtistImages(arg1:string[]):Promise<Record<string, string>>;
-
-export function GetArtistMBID(arg1:string):Promise<string>;

frontend/wailsjs/go/explore/Service.js

@@ -10,6 +10,10 @@ export function BrowseReleases(arg1) {
   return window['go']['explore']['Service']['BrowseReleases'](arg1);
 }
 
+export function CheckLibraryMBIDs(arg1) {
+  return window['go']['explore']['Service']['CheckLibraryMBIDs'](arg1);
+}
+
 export function CoverArtGroupURL(arg1) {
   return window['go']['explore']['Service']['CoverArtGroupURL'](arg1);
 }
@@ -22,6 +26,10 @@ export function GetArtistImageURL(arg1) {
   return window['go']['explore']['Service']['GetArtistImageURL'](arg1);
 }
 
+export function GetArtistMBID(arg1) {
+  return window['go']['explore']['Service']['GetArtistMBID'](arg1);
+}
+
 export function GetThumbnail(arg1, arg2, arg3) {
   return window['go']['explore']['Service']['GetThumbnail'](arg1, arg2, arg3);
 }
@@ -30,6 +38,10 @@ export function GetThumbnails(arg1) {
   return window['go']['explore']['Service']['GetThumbnails'](arg1);
 }
 
+export function InvalidateIndexDiscographies() {
+  return window['go']['explore']['Service']['InvalidateIndexDiscographies']();
+}
+
 export function LookupArtist(arg1) {
   return window['go']['explore']['Service']['LookupArtist'](arg1);
 }
@@ -62,14 +74,18 @@ export function SimilarArtists(arg1) {
   return window['go']['explore']['Service']['SimilarArtists'](arg1);
 }
 
+export function StartIndexBuild() {
+  return window['go']['explore']['Service']['StartIndexBuild']();
+}
+
+export function StopIndexBuild() {
+  return window['go']['explore']['Service']['StopIndexBuild']();
+}
+
 export function TopRecordingsForArtist(arg1) {
   return window['go']['explore']['Service']['TopRecordingsForArtist'](arg1);
 }
 
-export function CheckLibraryMBIDs(arg1) {
+export function GetArtistImages(arg1) {
-  return window['go']['explore']['Service']['CheckLibraryMBIDs'](arg1);
+  return window['go']['explore']['Service']['GetArtistImages'](arg1);
-}
-
-export function GetArtistMBID(arg1) {
-  return window['go']['explore']['Service']['GetArtistMBID'](arg1);
 }