feat: build driver repayment center

[OkeyAmy]

Closes #44

Summary

• Added centralized repayment schedule, arrears, ownership progress, and overpayment calculations to the driver contract service.
• Expanded the driver repayment page with empty state messaging, late/current status alerts, repayment schedule table, active contract summary, overpayment notice, and repayment history.
• Updated repayment summary/history components to display total contract amount, outstanding balance, applied payment amounts, and overpayment credits.

Testing

• npm run lint
• npm run build

Notes

• Build completed with existing third-party/package warnings for missing optional @stripe/crypto resolution in Privy, viem dynamic dependency warnings, and duplicate Mongoose index warnings.