Fix: Prevent dismiss on barrier tap for alert dialog

[durannumit]

Description

This PR addresses an issue where alert dialogs could be dismissed by tapping the barrier (the area outside the dialog). This behavior was unintended for alert dialogs, which typically require explicit user action to dismiss.

Before Dismiss on Barrier	After Dismiss on Barrier

Checklist

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• [x] I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• [x] My PR includes tests for all changed/updated/fixed behaviors.
• [ ] All existing and new tests are passing.
• [x] I updated/added relevant documentation (doc comments with ///).
• [x] The analyzer (melos run analyze) does not report any problems on my PR.
• [x] The package compiles with the minimum Flutter version stated in the pubspec.yaml

Breaking Change

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• [ ] Yes, this is a breaking change.
• [x] No, this is not a breaking change.

[github-actions[bot]]

Visit the preview URL for this PR (updated for commit aea7e69):

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