prober: on-screen + in-report build number (versionCode, now 2)

Ascending integer bumped per deployed change; shown in the header and as
proberBuild in the JSON report so a report is attributable to an exact
build. buildConfig feature enabled for BuildConfig.VERSION_CODE.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

echolot-prober/app/build.gradle.kts

@@ -13,7 +13,9 @@ android {
         applicationId = "app.echo_lot.prober"
         minSdk = 26
         targetSdk = 35
-        versionCode = 1
+        // Bump versionCode on EVERY deployed change — it is shown on screen and lands in the
+        // JSON report as proberBuild, so a report is attributable to an exact prober build.
+        versionCode = 2
         versionName = "0.1.0"
     }
 
@@ -32,6 +34,7 @@ android {
     buildFeatures {
         compose = true
         aidl = true
+        buildConfig = true // BuildConfig.VERSION_CODE feeds the on-screen + report build number
     }
 }