[andryan0001]

Summary

Adds saved filter presets to the dynamic filter sheet used by external/Mihon sources.

• Add a Save button and saved-filter chips to the external filter sheet.
• Reuse SavedFiltersRepository / PersistableFilter; no storage migration needed.
• Add shared SavedFilterActions for save, overwrite, rename, and delete dialogs.
• Keep dynamic source sort separate: presets exclude the sort tag and applying one preserves the active sort.
• Match dynamic presets by encoded filter keys, ignoring tag titles/source and sort.
• Normalize tag sources during plugin-key migration.
• Reload the embedded/tablet filter sheet when filters change externally.
• Add filter unit tests.

Closes #158.

Testing

• Debug APK built successfully with GitHub Actions (assembleDebug).
• New FilterMapperTest and MangaListFilterSerializerTest pass.
• Tested save, apply, rename, delete, and overwrite with a dynamic external source using the debug APK.

Note: the full unit test task still fails on the pre-existing VersionIdTest.testCurrentVersion because it expects an app version greater than 2.4.6 while the current version is 2.0-beta1. The new filter tests pass independently.