test: improve test coverage to >75%

[ElvinGts]

Fixes #71.

Summary

As requested in the bounty, this PR drastically improves the test coverage across the entire project.

I have added meaningful tests for the main router (index.ts), operations (operation.ts), hander edge cases (handler.ts), RLS queries (rls/index.ts), allowlist operations, LiteREST, and CSV import logic.

All external services (Postgres, MySQL, LibSQL, Cloudflare Workers, Jose) are properly mocked to ensure tests are isolated and reliable. Tested against various edge cases including null values, fake table names, and invalid inputs.

Coverage Achieved

• Statements: ~93.16%
• Branches: ~75.15%
• Functions: ~93.78%
• Lines: ~93.41%

Ready for review and Algora bounty processing.

[ElvinGts]

Hi team! 👋 Just following up on this bounty submission. I've successfully pushed the coverage to >93% as requested, with all external dependencies mocked for clean isolation. Let me know if everything looks good to merge so the Algora bounty can be processed! 🚀