fix(mobile): use immutable cache keys for local images (#17736)

fix(mobile): usse immutable cache keys for local images

mobile/lib/providers/image/immich_local_image_provider.dart

@@ -106,12 +106,12 @@ class ImmichLocalImageProvider extends ImageProvider<ImmichLocalImageProvider> {
   bool operator ==(Object other) {
     if (identical(this, other)) return true;
     if (other is ImmichLocalImageProvider) {
-      return asset == other.asset;
+      return asset.id == other.asset.id;
     }
 
     return false;
   }
 
   @override
-  int get hashCode => asset.hashCode;
+  int get hashCode => asset.id.hashCode;
 }

mobile/lib/providers/image/immich_local_thumbnail_provider.dart

@@ -89,11 +89,14 @@ class ImmichLocalThumbnailProvider
 
   @override
   bool operator ==(Object other) {
-    if (other is! ImmichLocalThumbnailProvider) return false;
     if (identical(this, other)) return true;
-    return asset == other.asset;
+    if (other is ImmichLocalThumbnailProvider) {
+      return asset.id == other.asset.id;
+    }
+
+    return false;
   }
 
   @override
-  int get hashCode => asset.hashCode;
+  int get hashCode => asset.id.hashCode;
 }