feat(app): in-app asset picker (wechat_assets_picker) - unlimited multi-select with range selection

Review fixes: per-asset originFile error isolation (failed asset skipped, not whole batch); drop maxSdkVersion from READ_MEDIA_VISUAL_USER_SELECTED (API 34+, no upper bound); originFile doc accuracy (API 30+ direct path vs Android 10 ScopedCache copy).

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

apps/mobile/test/pages/album_detail_page_test.dart

@@ -336,7 +336,7 @@ void main() {
               client: clientOf(adapter),
             ),
             multiImagePickerProvider
-                .overrideWith((ref) => () async => galleryPaths),
+                .overrideWith((ref) => (context) async => galleryPaths),
             uploadPreparerProvider.overrideWith(
               (ref) => UploadPreparer(
                 taskStore,

apps/mobile/test/pages/capture_page_test.dart

@@ -177,7 +177,7 @@ void main() {
             (ref) => NotificationPermission(isAndroid: false),
           ),
           multiImagePickerProvider
-              .overrideWith((ref) => () async => galleryPaths),
+              .overrideWith((ref) => (context) async => galleryPaths),
         ],
         child: MaterialApp(
           localizationsDelegates: AppLocalizations.localizationsDelegates,