feat: add APort Zapier verification app

[KingParmenides]

Summary

• Adds a Zapier CLI custom app under examples/platform-integrations/zapier with an APort Verify action.
• Supports custom auth with optional bearer token/base URL, request hooks, and denial handling.
• Documents setup, publish flow, action inputs/outputs, and includes an example refund-verification Zap blueprint.

Verification

• npm_config_cache=/private/tmp/codex-npm-cache npm test
• XDG_CONFIG_HOME=/private/tmp/codex-config npm_config_cache=/private/tmp/codex-npm-cache npx zapier-platform validate
• git diff --check

Closes #6

Bounty: $50 USD
Preferred payout: BTC 39Q34P8A7g375yqEr8buvNJkUbRgKfbKQZ