feat: add build-info footer with version, commit SHA, and network (#952)

[temisan0x]

Closes #952

What changed

• added build-time env injection for:
  • app version
  • commit SHA
  • Stellar network
• added BuildInfoFooter component
• mounted footer in [locale]/layout.tsx
• added i18n keys for footer labels
• documented new env vars in .env.example

Notes

• commit SHA falls back to local if git metadata is unavailable
• backend /version support left for [Backend] Add GET /version endpoint exposing build SHA, build time, and contract IDs #881

Testing

• npm run build
• verified footer renders correctly

[temisan0x]

hey @ogazboiz, the backend and frontend failures are pre-existing on main — loanEndpoints, webhookRetryProcessor, and amount.test.ts are all untouched by this PR. Please let me know if you want me to rebase once those are sorted upstream

[ogazboiz]

hey, please rebase to pick up recent main changes — your CI is failing on issues that main has since resolved.

git fetch upstream
git rebase upstream/main
git push --force-with-lease