chore: Halkyon Learn moves into apps/learn

Its server, client, app and curator, and the tools that write its
assets (maps, Anki fixtures, icons), as they are; paths are fixed in
the commits that follow.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/android/app/build.gradle.kts

@@ -1,90 +0,0 @@
-plugins {
-    id("com.android.application")
-    // The Flutter Gradle Plugin must be applied after the Android and Kotlin Gradle plugins.
-    id("dev.flutter.flutter-gradle-plugin")
-}
-
-android {
-    namespace = "app.halkyon.learn"
-    compileSdk = flutter.compileSdkVersion
-    ndkVersion = flutter.ndkVersion
-
-    compileOptions {
-        sourceCompatibility = JavaVersion.VERSION_17
-        targetCompatibility = JavaVersion.VERSION_17
-    }
-
-    defaultConfig {
-        applicationId = "app.halkyon.learn"
-        // You can update the following values to match your application needs.
-        // For more information, see: https://flutter.dev/to/review-gradle-config.
-        minSdk = flutter.minSdkVersion
-        targetSdk = flutter.targetSdkVersion
-        // Uses the version code from pubspec.yaml. When using split APKs, 1000 * ABI_VERSION
-        // is added automatically by Flutter. (https://developer.android.com/studio/build/configure-apk-splits#configure-APK-versions)
-        // You can force using the value of versionCode by specifying the `-P force-version-code-ignoring-abi=true`
-        // flag during build.
-        versionCode = flutter.versionCode
-        versionName = flutter.versionName
-    }
-
-    // The app's own key signs release builds when tool/release.sh hands it over
-    // through the environment: the keystore's path and the key's alias, and the
-    // password asked for at each release, never written down. Other release builds
-    // are signed with the debug key, so `flutter run --release` works anywhere; the
-    // release script refuses to build without the app's key.
-    val releaseKeystore = System.getenv("HALKYON_ANDROID_KEYSTORE")
-    signingConfigs {
-        if (releaseKeystore != null) {
-            create("release") {
-                storeFile = file(releaseKeystore)
-                keyAlias = System.getenv("HALKYON_ANDROID_KEY_ALIAS")
-                // A PKCS #12 keystore has one password, for the store and its key.
-                storePassword = System.getenv("HALKYON_ANDROID_KEYSTORE_PASSWORD")
-                keyPassword = System.getenv("HALKYON_ANDROID_KEYSTORE_PASSWORD")
-            }
-        }
-    }
-
-    buildTypes {
-        release {
-            signingConfig =
-                signingConfigs.findByName("release") ?: signingConfigs.getByName("debug")
-        }
-    }
-
-    // The native libraries go into the APK compressed. One APK serves every phone, so
-    // it holds them for three architectures; stored uncompressed (the default, made
-    // for stores that send each phone its own) they made it 110 MB to download and to
-    // keep. Compressed it's about half that, and Android unpacks the phone's own
-    // libraries as it installs the app.
-    packaging {
-        jniLibs {
-            useLegacyPackaging = true
-        }
-    }
-
-    // Leaves out the list of dependencies Gradle would otherwise add to the APK,
-    // encrypted for Google Play alone; F-Droid's and others' scanners flag it.
-    dependenciesInfo {
-        includeInApk = false
-        includeInBundle = false
-    }
-}
-
-kotlin {
-    compilerOptions {
-        jvmTarget = org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17
-    }
-}
-
-flutter {
-    source = "../.."
-}
-
-dependencies {
-    // NotificationCompat's ProgressStyle and promoted notifications (Android 16's
-    // Live Updates) for the Pomodoro timer, from v1.17 on; the build resolves this
-    // version already. v1.19 would need compileSdk 37.
-    implementation("androidx.core:core:1.18.0")
-}