new: persist preferences across sessions

data/preferences/build.gradle.kts

@@ -3,7 +3,27 @@ plugins {
 }
 
 kotlin {
+    // Adding custom `dependsOn` edges below disables the automatic default hierarchy, so re-apply it
+    // explicitly to keep the standard commonMain/appleMain/iosMain/webMain wiring.
+    applyDefaultHierarchyTemplate()
+
     androidLibrary {
         namespace = "fr.ajaury.gwenedeg.preferences"
     }
+
+    sourceSets {
+        // Persistence via DataStore for every target that has an artifact for it (Android, iOS,
+        // Desktop). Web (JS/Wasm) has no DataStore artifact, so it keeps commonMain's in-memory
+        // implementation.
+        val dataStoreMain by creating {
+            dependsOn(commonMain.get())
+            dependencies {
+                implementation(libs.androidx.datastore.preferences.core)
+                implementation(libs.okio)
+            }
+        }
+        androidMain.get().dependsOn(dataStoreMain)
+        jvmMain.get().dependsOn(dataStoreMain)
+        iosMain.get().dependsOn(dataStoreMain)
+    }
 }