Implement automatic fee normalization and rounding

[Just-Bamford]

Problem

Fee estimates from \src/transaction/estimateFee.ts\ return precise values, but Stellar requires stroops (smallest unit). Rounding inconsistencies between client and server can cause submission failures. No normalization utility exists.

Solution

Add
ormalizeFee(fee: string | number)\ utility in \src/shared/utils.ts\ that ensures fees are integers in stroops, with proper rounding. Use throughout fee estimation and transaction building.

Acceptance Criteria

• 
  ormalizeFee()\ added to \src/shared/utils.ts\
• Accepts string or number, returns integer stroops
• Implements proper rounding (banker's rounding or floor)
• \estimateFee()\ uses normalization before returning
• Transaction builders use normalized fees
• Tests added covering decimal, string, edge cases
• Export in \src/shared/index.ts\

Note for contributors

Reference Stellar's stroop definition (1 XLM = 10,000,000 stroops). Test rounding edge cases. Add tests to \src/tests/shared.test.ts.

[Sam-Rytech]

@Sam-Rytech has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hey maintainer

I'd like to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Sam-Rytech to this issue.

[drips-wave]

Congratulations, @codewithzubair07! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

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