feat(android): split release APK per ABI for F-Droid

Adds a versionCodeOverride to build.gradle.kts (F-Droid requires distinct
versionCodes per split APK; Google Play's App Bundle is unaffected since
this only touches the application-variant/APK output). Bumps to 0.1.2+4.

Verified locally: flutter build apk --release --split-per-abi produces
app-{armeabi-v7a,arm64-v8a,x86_64}-release.apk with versionCode 31/32/33.

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

@@ -85,3 +85,21 @@ dependencies {
     // Backport of Java 8+ APIs, required by flutter_local_notifications.
     coreLibraryDesugaring("com.android.tools:desugar_jdk_libs:2.1.4")
 }
+
+// F-Droid builds one split APK per ABI (smaller downloads than a universal
+// APK) and needs each split to carry a distinct versionCode so its repo can
+// tell them apart; `flutter build apk --split-per-abi` alone gives every
+// split the same versionCode. This override only touches the APK
+// (applicationVariants) output, not the App Bundle Google Play consumes, so
+// Play's per-device delivery is unaffected.
+val abiVersionCodes = mapOf("armeabi-v7a" to 1, "arm64-v8a" to 2, "x86_64" to 3)
+android.applicationVariants.all {
+    val variant = this
+    variant.outputs.all {
+        val output = this as com.android.build.gradle.internal.api.ApkVariantOutputImpl
+        val abi = output.getFilter(com.android.build.OutputFile.ABI)
+        abiVersionCodes[abi]?.let { abiCode ->
+            output.versionCodeOverride = variant.versionCode * 10 + abiCode
+        }
+    }
+}