feat: data persistence module with transactions, migrations and audit…

[a-malik-gh]

… trail for issue #12

Summary

Related Issues

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that changes existing behaviour)
• Documentation only
• Refactor / chore (no functional change)

Changes

Checklist

• I have read the CONTRIBUTING guide.
• npm run lint passes.
• npx tsc --noEmit passes (no type errors).
• npm run build succeeds.
• npm test passes, and I added/updated tests for my change where it
  made sense.
• Any Stellar/Soroban network access goes through the stellar module
  services (no direct Horizon/RPC calls from feature modules).
• I did not commit secrets, private keys, or mainnet credentials.

Notes for Reviewers

[ykargeee-bit]

👋 Thanks for the contribution! This PR currently has merge conflicts with the base branch and the CI build is failing. Could you rebase/merge the latest changes from main and push a fix for the build when you have a moment? This is a substantial feature (data persistence module with transactions, migrations, and audit trails) that will need manual conflict resolution and review.