feat: implement Redis-based rate limiting (100 req/min)

[Chidubemkingsley]

Description

Closes #37

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📝 Documentation update
• 🔧 Configuration change
• ♻️ Code refactoring
• ⚡ Performance improvement
• ✅ Test update

Component

• Backend (Node.js API)
• Frontend (Next.js UI)
• Smart Contract (Soroban/Rust)
• SDK
• Infrastructure/DevOps
• Documentation

Testing

Manual Testing

• Tested locally
• Tested in development environment
• Tested edge cases

Automated Testing

• Unit tests added/updated
• Integration tests added/updated
• All tests passing locally

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

[meshackyaro]

Great work and well done!