test: add comprehensive unit tests for rate-limiter and url-shortener

[oniani1]

Summary

• Add unit tests for 6 untested rate-limiter files: RuleManagerService, AlgorithmManagerService, ClientIdentifierService, RateLimiterService, RateLimitGuard, and exectRedisScriptSha helper
• Add unit tests for 4 untested url-shortener files: UrlRepository, ShortenUrl command handler, GetRealUrl query handler, and BatchCounterService
• Fix broken Jest configs in both apps by converting .ts to .cts (ESM __dirname issue)

135 total tests passing (44 rate-limiter + 91 url-shortener), 0 failures.

Linked Issues

N/A

Checklist

• Tests added/updated (if relevant)
• Documentation updated (if relevant)
• Linting and formatting pass
• Ready for review

Additional Context

• All test files follow the existing *.spec.ts convention and sit alongside their source files
• Tests use Jest with mocked dependencies (no NestJS TestingModule needed for pure unit tests)
• Jest config fix: .ts → .cts conversion matches the pattern already used by rate-limiter's jest.config.cts and aligns with NX's official convert-jest-config-to-cjs migration
• No existing source files were modified — only new test files and config fixes

[CSenshi]

1. Remove all 4 jest config changes - jest.config.ts already works on main (existing unit tests prove it). None of the new tests need the .cts conversion.
2. Remove the redundant guard test - "should propagate RateLimitExceededException from check" tests an impossible path. The guard creates and throws RateLimitExceededException itself based on result.allowed; rateLimiterService.check never throws it. The ECONNREFUSED test above already covers error propagation.

[oniani1]

Removed the redundant guard test --rateLimiterService.check returns a result object and the guard itself throws RateLimitExceededException based on result.allowed. The ECONNREFUSED test already covers error propagation.

On the jest configs though -- reverting them back to .ts breaks the url-shortener tests with ReferenceError: __dirname is not defined in ES module scope. Cleared the Nx cache and confirmed it's not a caching issue. The rate-limiter's jest.config.cts is already .cts on main for the same reason, so the .cts conversion seems necessary for any config that uses __dirname. Happy to look into an alternative fix if you'd prefer not to have the .cts files, but reverting them as-is breaks the test runs.

[CSenshi]

LGTM