fix(images): cancel orphaned thumbnail downloads

[NotThatKindOfDrLiz]

Closes #4692
Closes #4696

Summary

• replace the last cached_network_image usage with a repo-owned MediaCacheImageProvider backed by MediaCacheManager.cacheFileCancellable
• cancel in-flight thumbnail downloads when the last image listener is removed while preserving VineCachedImage's public API
• drop the cached_network_image dependency and refresh regression coverage around avatars, thumbnails, and concurrent image loading

Verification

• flutter test test/src/media_cache_image_provider_test.dart (from mobile/packages/media_cache)
• flutter test --no-pub test/widgets/vine_cached_image_test.dart
• flutter test --no-pub test/widgets/video_thumbnail_widget_test.dart
• flutter test --no-pub test/widgets/comprehensive_user_avatar_test.dart
• flutter test --no-pub test/notifications/widgets/notification_avatar_stack_test.dart
• flutter test --no-pub test/widgets/ios_network_image_deadlock_test.dart
• flutter test --no-pub test/widgets/profile/profile_tab_thumbnail_test.dart
• flutter test --no-pub test/widgets/user_avatar_svg_test.dart
• flutter analyze --no-pub lib/widgets/vine_cached_image.dart packages/media_cache/lib/src/media_cache_image_provider.dart packages/media_cache/test/src/media_cache_image_provider_test.dart test/widgets/ios_network_image_deadlock_test.dart test/widgets/video_thumbnail_widget_test.dart test/widgets/comprehensive_user_avatar_test.dart test/notifications/widgets/notification_avatar_stack_test.dart test/widgets/vine_cached_image_test.dart test/widgets/profile/profile_tab_thumbnail_test.dart

Notes

• full-repo flutter analyze still reports pre-existing infos in unrelated manual/integration scripts outside this diff; the changed files above analyze cleanly
• flutter test / flutter analyze without --no-pub can crash in this worktree because Flutter tries to delete ios/Flutter/ephemeral/Packages/.packages; verification used the already-resolved dependency graph to avoid that tooling bug

[rabble]

Found one issue that I think should be fixed before merge.

• mobile/packages/media_cache/lib/src/media_cache_image_provider.dart:149: operator == compares authHeaders by contents with mapEquals, but hashCode hashes the MapEntry objects from authHeaders.entries. MapEntry equality/hash is identity-based, so two providers with equal header maps can compare equal while producing different hash codes. Since this class is an ImageProvider key, that violates the key contract used by Flutter's ImageCache and can lead to duplicate/missed cache entries when callers pass equivalent header maps. Please hash headers by stable key/value pairs, for example sorted entries or Object.hashAllUnordered(entries.map((e) => Object.hash(e.key, e.value))), and add a regression test for equal providers with separate but equal header maps.

Verification I ran locally from mobile/:

• flutter test packages/media_cache/test/src/media_cache_image_provider_test.dart test/widgets/vine_cached_image_test.dart

[hm21]

LGTM. I left only one minor nit comment but nothing blocking. I also tested it on android and it works perfectly fine for me.

[github-actions]

Mobile PR Preview

Preview refreshed for 5a6bb6e

Last refresh: 5a6bb6e at 2026-05-25 15:22:53 UTC (preview run)

Property	Value
Preview URL	https://f3a82eb5.openvine-app.pages.dev
Pages project	openvine-app
Preview branch	pr-4695
PR branch	fix/profile-thumbnail-cancellation
Commit	5a6bb6e

[NotThatKindOfDrLiz]

Addressed the review feedback in commit 5a6bb6e.

Changes in this update:

• fixed MediaCacheImageProvider.hashCode so authHeaders hashes by stable key/value pairs and now matches the existing mapEquals equality semantics
• added regression coverage for equal providers built from separate-but-equal header maps, plus assertions that cacheKey and scale still distinguish keys
• extracted the new placeholder and error helpers in VineCachedImage into private widget classes to match the repo widget-composition rule

Local verification on this revision:

• flutter analyze lib test integration_test packages/media_cache
• flutter test packages/media_cache/test/src/media_cache_image_provider_test.dart
• flutter test test/widgets/vine_cached_image_test.dart test/widgets/video_thumbnail_widget_test.dart test/widgets/ios_network_image_deadlock_test.dart
• the repo pre-push hook also passed its changed-file analyzer/test gate before push

[NotThatKindOfDrLiz]

@rabble Can you please re-review and clear your requested changes? Thanks!