fix: sync vendor registry contract client

[Davidemulo]

Summary

Closes #96

Synchronizes the vendor-registry client with the deployed Soroban contract so vendor checks use the current function names, Stellar Address arguments, and typed status model. It also narrows missing-vendor handling to contract error code 4 so integration drift is logged and fails loudly.

This repo is for the NestJS backend API only

• My changes are inside src/ or test/ (plus the mandatory progress tracker)
• I have NOT added React, React Native, or frontend component files
• I have NOT added Rust or Soroban contract code
• This is NestJS/TypeScript backend work

Type of change

• Bug fix
• New endpoint
• New service or module
• Database migration
• Background job
• Test coverage

Changes Made

• Invoke is_active and get_vendor_info with Address ScVals
• Replace the stale active boolean with the Pending/Approved/Suspended/Rejected VendorStatus union
• Reject unknown status values and rethrow non-vendor-not-found contract failures as ContractReadError
• Update the vendor mock and public type exports
• Add client-level tests for exact function names, address encoding, status validation, and error handling
• Update context/progress-tracker.md

Testing

• npm run build passes with zero TypeScript errors
• npm test passes — 29 suites and 322 tests
• No new any types introduced anywhere
• Swagger decorators not applicable — no endpoints changed
• Migration not applicable — no schema changes
• New unit tests cover the changed client behavior

Commands run:

• npm run build
• npm test -- --runInBand
• npx eslint on all changed TypeScript files

Context files reviewed

• context/architecture-context.md
• context/code-standards.md
• context/progress-tracker.md updated

The current StepFi-Contracts vendor-registry lib.rs, types.rs, and errors.rs were also reviewed to confirm the deployed signatures, status variants, and VendorNotFound error code.