feat(train): Health Connect's bridge, in Kotlin of Train's own (ADR 0030, D30)

connect-client 1.1.0 behind app.halkyon.train/health: its status, the
permissions by the app's three names (write, read, history), Train's
records written by their client IDs and deleted by them, other apps'
sessions read through the changes token or whole, their samples, and a
route with the person's consent; the rationale's links from Health
Connect. Android 8 at least now, as the client needs it. The records'
mapping is tested on the JVM, the channel's encoding in Dart; the fake
platform is for the parts to come.

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

apps/train/halkyon_train_flutter/android/app/build.gradle.kts

@@ -19,7 +19,8 @@ android {
         applicationId = "app.halkyon.train"
         // 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
+        // Android 8: Health Connect's client needs it (ADR 0030, D31).
+        minSdk = 26
         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)
@@ -52,6 +53,8 @@ dependencies {
     // NotificationCompat and ServiceCompat for the recording's foreground service,
     // the version Learn's build uses.
     implementation("androidx.core:core:1.18.0")
+    // Health Connect (ADR 0030, D30, D31): AndroidX's client, no Play services.
+    implementation("androidx.health.connect:connect-client:1.1.0")
     // The recorder's pure Kotlin parts (auto-pause) tested on the JVM.
     testImplementation("junit:junit:4.13.2")
 }