feat: add standalone React audit trail viewer

[bbbbzzzzcc-afk]

Summary

• add @nirium/audit-trail-viewer as a standalone typed React package
• request anchored receipts from GET /api/audit/info using the required app_id
• render IPFS and Stellar Expert links with a precompiled Tailwind stylesheet that omits global preflight styles
• support loading, empty, error, configurable API/gateway/network, and common response envelopes
• include ESM, CommonJS, declarations, package exports, and usage documentation

The referenced source component is not present in the public repository history, so this is a clean-room implementation limited to the acceptance criteria.

Validation

• npm run check — production build and 7 tests passed
• npm audit --omit=dev --audit-level=high — 0 vulnerabilities
• npm pack --dry-run — package contents verified with no bundled dependencies
• ESM and CommonJS export smoke checks passed
• git diff --check passed

Closes #12

GrantFox bounty: $50 USDC standalone React AuditTrail Viewer widget.