feat(format): add compact large-number formatter

[Truphile]

Summary of Work

1. Compact Formatter (formatCompactNumber & formatCompactNumberDisplay):
   • Added locale-aware compact number formatter helpers using Intl.
   NumberFormat in format.ts.
   • Handles magnitudes: K, M, B, zero, negative values, and non-finite
   numbers while preserving the raw precise value in title and aria-label.
2. Pairs and Stats Views Integration:
   • Applied compact formatting to pair volume in PairsDrawer.tsx and
   pairs count badge in Client.tsx.
   • Applied compact formatting to StatTile.tsx and router metrics in
   Client.tsx, exposing full precise values via title and aria-label.
3. Comprehensive Unit Test Coverage:
   • Added unit tests covering small numbers, rounding boundaries at K, M,
   B, zero, negative values, non-finite numbers, and custom locale
   formatting in format.test.ts.
   • Updated component and page unit tests in PairsDrawer.test.tsx and
   page.test.tsx.
4. Verification:
   • Ran npm test: 71 passed, 71 total (1071/1071 individual tests passed).
   • Ran npm run lint: 0 errors or warnings.
   • Ran npm run build: Compiled static production build successfully.

closes #482

[mikewheeleer]

@Truphile this is clean and complete. merging, thank you! ✨