fix(android): enable core library desugaring for flutter_local_notifications

apps/app_seeds/android/app/build.gradle.kts

@@ -25,6 +25,8 @@ android {
     ndkVersion = flutter.ndkVersion
 
     compileOptions {
+        // Required by flutter_local_notifications (uses Java 8+ APIs on older SDKs).
+        isCoreLibraryDesugaringEnabled = true
         sourceCompatibility = JavaVersion.VERSION_17
         targetCompatibility = JavaVersion.VERSION_17
     }
@@ -71,3 +73,8 @@ android {
 flutter {
     source = "../.."
 }
+
+dependencies {
+    // Backport of Java 8+ APIs, required by flutter_local_notifications.
+    coreLibraryDesugaring("com.android.tools:desugar_jdk_libs:2.1.4")
+}