feat: harden Restana 6.1 performance, ergonomics, and security

[jkyberneees]

Summary

• harden server lifecycle, response streaming, error disclosure, proxy trust, and response headers
• fix boolean bodies, array headers, cache disabling, configuration snapshots, and APM middleware registration
• add reproducible installs, expanded CI, TypeScript 7 declaration tests, meaningful performance budgets, and corrected benchmark methodology
• publish Restana 6.1 release notes, API guidance, contributor docs, npm-visible documentation, and accessibility improvements
• update the landing page with a dedicated v6.1 release section and safe configuration examples

Validation

• Node 24: lint, TypeScript declarations, 142 tests, and 95.88% line coverage pass
• GitHub Actions tests pass on Node 24 and Node 26
• clean npm ci succeeds
• production dependency audit: 0 vulnerabilities
• npm package dry run includes license and linked documentation
• full response, stream, promise, and route-scale benchmarks pass
• CI performance gate compares framework routing directly to the underlying router

Adversarial review

• code review issue fixed: npm-relative documentation links now ship in the package
• security review found no medium, high, or critical vulnerabilities; suggested array-header and stream-error cases added
• performance review rejected a measured 0http 5 regression and caught an attempted wrapper regression before release
• final performance verification reports +1.9% static / +2.8% parameterized routing versus master (measurement noise), with no release blockers