refactor(prefs): create the settings store through DataStore.Builder

The store is now built through DataStore.Builder instead of the
preferencesDataStore delegate.

README.md

@@ -89,7 +89,7 @@ The main search screen remains usable as long as at least one indexed dictionary
 - Jetpack Compose (BOM 2026.09.00)
 - Material 3 1.5.0-beta01
 - Coroutines and Flow 1.11.0
-- DataStore Preferences 1.2.1
+- DataStore Preferences 1.3.0
 - Paging 3.5.3
 - OkHttp 5.5.0
 - kotlinx.serialization 1.12.0