refactor(deps): replace url-parse with native URL API

[Kyzgor]

Summary

Remove the url-parse dependency in favor of the native URL class, which has been available since Node.js v10 — the SDK's minimum supported version.

Problem

As reported in #106, url-parse is an unnecessary third-party dependency. Node.js natively supports the URL class since v10, making this package redundant and adding unnecessary weight to the bundle.

Solution

Replaced all url-parse usage in src/enforcement/enforcer.ts with the native URL API:

• opaBaseUrl.set('port', '8181') → opaBaseUrl.port = '8181'
• opaBaseUrl.set('pathname', ...) → opaBaseUrl.pathname = ...
• .toString() — works identically on both

Changes

• src/enforcement/enforcer.ts — Removed url-parse import, replaced .set() calls with native property assignment
• package.json — Removed url-parse from dependencies and @types/url-parse from devDependencies
• yarn.lock — Regenerated without url-parse

Testing

• yarn lint — passes (0 errors)
• yarn build — succeeds (both CJS and ESM)
• yarn test:module-imports — all 9 tests pass
• Manual CJS verification: node -e "const { Permit } = require('./build'); console.log(typeof Permit);" → function

Backwards Compatibility

No breaking changes. Fully backwards-compatible. The native URL API has identical behavior for the operations used (constructor, port/pathname assignment, toString).

Checklist

• yarn lint passes
• yarn build succeeds (both CJS and ESM)
• yarn test:module-imports passes
• No changes to src/openapi/ (auto-generated)

Fixes #106