fix(feedback): prevent stacking multiple feedback dialogs on repeated shakes

Track dialog visibility with an isDialogShowing flag that is set before
showing and cleared via the onFormClose callback when the dialog is
dismissed. Double-checked on both sensor and UI threads to avoid races.

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

Author: antonis

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

@@ -26,6 +26,7 @@ public final class ShakeDetectionIntegration
   private @Nullable SentryShakeDetector shakeDetector;
   private @Nullable SentryAndroidOptions options;
   private volatile @Nullable Activity currentActivity;
+  private volatile boolean isDialogShowing = false;
 
   public ShakeDetectionIntegration(final @NotNull Application application) {
     this.application = Objects.requireNonNull(application, "Application is required");
@@ -102,12 +103,28 @@ private void startShakeDetection(final @NotNull Activity activity) {
         activity,
         () -> {
           final Activity active = currentActivity;
-          if (active != null && options != null) {
+          if (active != null && options != null && !isDialogShowing) {
             active.runOnUiThread(
                 () -> {
+                  if (isDialogShowing) {
+                    return;
+                  }
                   try {
+                    isDialogShowing = true;
+                    final Runnable previousOnFormClose =
+                        options.getFeedbackOptions().getOnFormClose();
+                    options
+                        .getFeedbackOptions()
+                        .setOnFormClose(
+                            () -> {
+                              isDialogShowing = false;
+                              if (previousOnFormClose != null) {
+                                previousOnFormClose.run();
+                              }
+                            });
                     options.getFeedbackOptions().getDialogHandler().showDialog(null, null);
                   } catch (Throwable e) {
+                    isDialogShowing = false;
                     options
                         .getLogger()
                         .log(SentryLevel.ERROR, "Failed to show feedback dialog on shake.", e);