Add precision regression tests for formatAmount/feeInBps with large Stellar amounts

[Jagadeeshftw]

📌 Description

formatAmount and feeInBps in src/lib/format.ts format numeric amounts for display across MetricsBar, StatCard, and the tables. Stellar amounts can carry seven decimal places of precision and large magnitudes; if these helpers pass values through plain JS Number arithmetic, values beyond Number.MAX_SAFE_INTEGER-adjacent ranges risk silent precision loss in the displayed figure.

🧩 Requirements and context

• Add tests for large amounts (e.g. near Number.MAX_SAFE_INTEGER) and high-precision decimal amounts, asserting the formatted output matches the expected exact string.
• If precision loss is confirmed for realistic Stellar-scale amounts, consider a string/bigint-safe formatting path as a follow-up (flag it in the issue rather than necessarily fixing it here if it requires an API/type change).
• Keep formatAmount's existing output format for typical/small amounts unchanged.

🛠️ Suggested execution

• Add the large/high-precision cases to src/lib/format.test.ts.
• If a real precision bug is found and fixable within format.ts's current number-based signature, fix it; otherwise document the limitation clearly in a code comment.

✅ Acceptance criteria

• Large and high-precision amounts are covered by tests with exact expected output.
• Any precision-loss bug found is either fixed or explicitly documented as a known limitation.
• Existing typical-amount formatting is unaffected.

🔒 Security notes

Display-only; a precision-loss bug here would mislead a user about an amount's exact value without affecting the actual on-chain/backend accounting.

📋 Guidelines

• Minimum 95% test coverage
• Clear documentation
• Timeframe: 96 hours

[devfoma]

Hello, I would love to take on this issue. I'm a software engineer with over 4 years experience. and i'm confident I can resolve this issue

[grantfox-oss]

🦊 GrantFox — @devfoma has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #78)
2. Your PR will be reviewed by the AnchorNet-Org maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🦊 GrantFox — @devfoma has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #78)
2. Your PR will be reviewed by the AnchorNet-Org maintainers

Good luck! Track your progress on GrantFox.