feat(lib): Add centralised amount formatting helper for consistent token rendering

[NUMBER72857]

Summary

Centralises all amount rendering in lib/formatAmount.ts so decimal places, locale formatting, and unit labels are consistent site-wide. Replace inline toFixed() / template literal calls in WebhookLog.tsx with these helpers.

Changes

• lib/formatAmount.ts:
  • formatAmount(raw, asset, stroops?): full label, asset-aware decimals (XLM=7, USDC=2)
  • formatAmountValue(): number only — for table cells where column header names the asset
  • formatAmountCompact(): K/M abbreviations for summary widgets
  • isZeroAmount(): zero-value predicate for conditional styling
• __tests__/formatAmount.test.ts: 16 tests covering all paths, edge cases, stroops conversion, NaN

Usage in WebhookLog.tsx

import { formatAmount } from '@/lib/formatAmount';
// Replace: {entry.amount} {entry.asset}
// With:    {formatAmount(entry.amount, entry.asset)}

Closes #105

[drips-wave]

@NUMBER72857 Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits