feat: add APort AP2 payment bridge

[KingParmenides]

Summary

• Adds a JavaScript AP2 bridge under examples/protocol-bridges/ap2 using @aporthq/sdk-node for APort passport policy authorization.
• Adds an AP2 REST client wrapper, policyTrace mapping, allow/deny handling, confirmation payload support, and a mocked local payment-flow demo.
• Documents environment variables, live usage, authorization flow, and AP2 responsibility boundaries.

Verification

• npm_config_cache=/private/tmp/codex-npm-cache npm install --no-audit --no-fund --package-lock=false
• npm_config_cache=/private/tmp/codex-npm-cache npm test
• npm_config_cache=/private/tmp/codex-npm-cache npm run example
• git diff --cached --check with a temporary Git index

Closes #11

Bounty: $50 USD
Preferred payout: BTC 39Q34P8A7g375yqEr8buvNJkUbRgKfbKQZ