Update com.newsblur to 13.12.0 (255)

Changes

Fixes #3762 (closed)

1. Fix broken auto-update detection

UpdateCheckData pointed to clients/android/NewsBlur/buildSrc/src/main/java/Config.kt, which was deleted in a version catalog migration after 13.8.0. Version info is now in app/build.gradle.kts.

This is why the checkupdates bot stopped detecting new versions after 13.8.0.

2. Updated build entry for 13.12.0

The prebuild steps needed updates for code changes since 13.8.0:

What changed	Old (13.8.0)	New (13.12.0)
Feed items list	FeedItemsList.java	FeedItemsList.kt (converted to Kotlin)
Login flow	LoginProgress.kt	viewModel/LoginRegisterViewModel.kt
Review code removal	Java sed patterns	Kotlin sed patterns (multiline)
Subscription refs	/cancel/d on PrefsRepo	/SubscriptionSyncService/d (more precise)

I am the upstream maintainer (@samuelclay). The sed commands were tested locally against the source. Happy to help if the build needs adjustments.