fix: stripe payments can fail due to payment amount rounding mismatch

[MrWeez]

Description

Fix for issue where Stripe payments was marked as cancelled even if they was processed due to payment amount rounding mismatch during validation

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Type of Change

• Bug fix
• New feature
• Breaking change
• Refactor / code quality
• Documentation
• Other:

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Testing

Stripe was tested with exact same settings as user that reported this issue has and no error appeared

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AI Assistance

• I used AI tools to assist with this contribution

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Checklist

• My PR targets the development branch
• Commit messages follow Conventional Commits
• Code follows PSR-12
• I have reviewed my own code
• I have tested all affected functionality
• No new warnings or errors introduced

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Legal

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under the terms of the project's
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and that I have read and agree to the
Code of Conduct.

[Copilot]

Pull request overview

This PR fixes Stripe webhook payment validation to avoid false cancellations when the stored payment total (in database units) rounds to a different minor-unit amount than the Stripe PaymentIntent reports.

Changes:

• Adjust Stripe webhook payload validation to compare amounts in Stripe minor units (e.g., cents) rather than converting Stripe amounts back into database units.
• Reuse the existing convertAmount(...) logic for computing the expected Stripe amount from the stored Payment::total_price.
• Remove the now-unused convertGatewayAmountToDatabaseUnits(...) helper.

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