Add revenue trial pricing guard

[jaasieldelgado131]

/claim #20

Summary

• Add a dependency-free revenue-trial-pricing-guard module for the Revenue Infrastructure bounty.
• Validate trial reuse, trial overruns, missing conversion evidence, expired coupons, coupon plan mismatch, consortium eligibility, unsafe coupon stacking, and total discount cap risk before invoice release.
• Emit deterministic RELEASE_INVOICE, REVIEW_BEFORE_RELEASE, or HOLD_INVOICE actions from synthetic billing fixtures only.

Reviewer Artifacts

• Demo JSON: revenue-trial-pricing-guard/artifacts/demo-output.json
• Markdown report: revenue-trial-pricing-guard/artifacts/reviewer-report.md
• Risk map SVG: revenue-trial-pricing-guard/artifacts/discount-risk-map.svg
• Demo video: revenue-trial-pricing-guard/artifacts/trial-pricing-guard-demo.mp4

Verification

• node revenue-trial-pricing-guard/test.js
• node revenue-trial-pricing-guard/demo.js
• git diff --check
• Demo MP4 read check: 60 frames, 12 fps, 960x540, 238752 bytes

Safety

• Synthetic fixtures only.
• No credentials, real customers, private billing data, payment processors, external APIs, wallets, or payout systems.