feat(mobile): platform thumbnail api (#20910)

mobile/pigeon/thumbnail_api.dart

@@ -0,0 +1,30 @@
+import 'package:pigeon/pigeon.dart';
+
+@ConfigurePigeon(
+  PigeonOptions(
+    dartOut: 'lib/platform/thumbnail_api.g.dart',
+    swiftOut: 'ios/Runner/Images/Thumbnails.g.swift',
+    swiftOptions: SwiftOptions(includeErrorClass: false),
+    kotlinOut:
+        'android/app/src/main/kotlin/app/alextran/immich/images/Thumbnails.g.kt',
+    kotlinOptions: KotlinOptions(package: 'app.alextran.immich.images'),
+    dartOptions: DartOptions(),
+    dartPackageName: 'immich_mobile',
+  ),
+)
+@HostApi()
+abstract class ThumbnailApi {
+  @async
+  Map<String, int> requestImage(
+    String assetId, {
+    required int requestId,
+    required int width,
+    required int height,
+    required bool isVideo,
+  });
+
+  void cancelImageRequest(int requestId);
+
+  @async
+  Map<String, int> getThumbhash(String thumbhash);
+}