fix(feedback): reset isDialogShowing on activity pause to prevent stuck flag

If showDialog silently fails (e.g. activity destroyed between post and
execution), isDialogShowing would stay true forever, permanently
disabling shake-to-feedback. Reset it in onActivityPaused since the
dialog cannot outlive its host activity.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: antonis

sentry-android-core/src/main/java/io/sentry/android/core/ShakeDetectionIntegration.java

@@ -74,6 +74,10 @@ public void onActivityPaused(final @NotNull Activity activity) {
     if (activity == currentActivity) {
       stopShakeDetection();
       currentActivity = null;
+      // Reset dialog flag — the dialog cannot outlive the activity, so if
+      // showDialog silently failed or the activity is finishing, clear the flag
+      // to avoid permanently blocking shake-to-feedback.
+      isDialogShowing = false;
     }
   }