Contract: Add safe rounding and precision conversion standards

[Junirezz]

Summary

Ensure rounding behavior is consistent and safe across contract calculations.

Problem

Different precision paths can produce inconsistent token values and user confusion.

Acceptance Criteria

• Standardize rounding rules for vault and fee calculations
• Add tests for decimal conversion edge cases
• Validate conversions near boundary values
• Document rounding behavior for integrators

[Prz-droid]

@Prz-droid has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Gm maintainer, Can i work on this issue
ETA - 48 hours

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[drips-wave]

Congratulations, @Prz-droid! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @Prz-droid: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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[drips-wave]

This issue has been completed by @Prz-droid as part of the Stellar Wave Program's 8th Wave 🥳

😎 @Prz-droid: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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