feat(shared): add opt-in diagnostics client with compile-time kill switch

Ship client-side telemetry, crash capture, and bug-report assembly behind a
user opt-in, with NoOp transport until Cloudflare is wired. Builds can set
vnidrop.diagnostics.included=false to omit the Share-diagnostics UI and
disable the telemetry/crash auto-upload stack while keeping bug reports.

gradle.properties

@@ -12,3 +12,9 @@ android.newDsl=false
 android.nonTransitiveRClass=true
 android.sourceset.disallowProvider=false
 android.useAndroidX=true
+
+# VniDrop: compile-time diagnostics/telemetry product surface.
+# false → no Share-diagnostics toggle, no telemetry or crash auto-upload stack.
+# Bug report UI remains available (user-initiated).
+# Override per build: ./gradlew … -Pvnidrop.diagnostics.included=false
+vnidrop.diagnostics.included=true