[sang765]

Summary

This draft PR adds direct Tachiyomi/Mihon extension management to Usagi without installing extension APKs as Android packages. Extensions are downloaded, loaded through a child-first DexClassLoader, and registered into the existing source manager.

Included

• Browse Tachiyomi/Mihon extensions in Source catalogs with language, source type, NSFW, and imported-plugin filters.
• Import, install, update, disable, enable, and remove direct extensions without PackageInstaller.
• Show installed Tachiyomi sources in Manage sources and imported repositories as one deduplicated row in Manage plugins.
• Support automatic repository catalog detection and latest-extension selection for external repositories.
• Display extension metadata and source icons using the configured source domain favicon.
• Handle content ratings across extension library versions and normalize regional language codes for catalog filters.
• Add Android 5 compatibility for compatible DEX 038 extensions by normalizing them to DEX 035.
• Fix Android 12+ read-only APK/DexClassLoader handling and preserve useful catalog loading diagnostics with copy-error support.
• Unload disabled Tachiyomi sources from the source catalog and cancel plugin update requests with the ViewModel lifecycle.
• Apply the related service resource-context leak fix and remove the redundant Source catalog add button.

Validation

• ./gradlew spotlessApply :app:assembleDebug --no-daemon
• Debug APK produced successfully at app/build/outputs/apk/debug/app-debug.apk.
• The branch was merged with the latest upstream/devel before pushing.