feat: add Stellar wallet and formatting helpers

[Rampop01]

Summary

• Add consistent token, percentage, compact-number, address, date, relative-time, and duration formatting helpers, and use the token formatter in the balance display.
• Add a unified Freighter, LOBSTR, and Rabet adapter with wallet detection, a provider chooser, provider persistence, selected-provider restoration, and transaction signing.
• Add Stellar SDK helpers for Horizon payments, Soroban contract invocation preparation, wallet signing, and RPC submission with status/error handling.
• Add focused tests for the formatters, wallet selection, transaction construction/submission, and selected-wallet restoration.

Validation

• npm ci --ignore-scripts --no-audit --no-fund
• Focused Vitest suite: 8 files, 52 tests passed.
• Changed-source ESLint and focused strict TypeScript checks passed.
• Production webpack compilation succeeded. The full build remains blocked by pre-existing repository issues: malformed src/lib/api/client.test.ts and src/lib/hooks/use-wallet-watcher.test.tsx lint parsing, and a verification.isValid/valid type mismatch in the credential page. The dedicated test tsconfig also currently excludes its own src/tests inputs.

Compatibility note

The frontend backend-auth flow verifies a signed message. The supported LOBSTR and Rabet integrations connect and sign transactions, but their current wallet APIs do not support message signing, so those wallets cannot complete JWT login until the backend supports an authentication method they expose. Freighter authentication remains supported.

Fixes #345
Fixes #346
Fixes #347
Fixes #348

[netlify]

❌ Deploy Preview for chainlearn failed.

Name	Link
🔨 Latest commit	fc58cca
🔍 Latest deploy log	https://app.netlify.com/projects/chainlearn/deploys/6abac0b38a43870008add279

[drips-wave]

@Rampop01 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