M8: Stripe billing + tier metering — $99 / $299 / Scale, usage hooks for image + video + SKU count

[ninan-versioning]

Milestone 8 — Billing & Metering

Vertical: enterprise
Revenue-Signal: acquisition
Customer-Type: smb-brand|mid-market|enterprise

What

Wire Stripe billing for $99 / $299 / Scale tiers, with usage metering hooks for image runs, video runs, and SKU count. Replaces the loose "licensing hooks" line in M4 with a shippable subscription product.

Scope

• Stripe products: shoploop_starter_99, shoploop_growth_299, shoploop_scale_custom
• Usage meters: image_runs, video_runs, active_skus (Stripe Usage-Based Billing API)
• Shopify Billing API parity: for App Store installs, billing flows via Shopify (merchant convenience); for direct accounts, Stripe
• Tier gates wired to M7 cost guardrails — over-tier requests get upsell modal, not silent failure
• Cancellation flow: data export triggered (see M9), then billing termination
• Annual plan: 20% discount, locked feature scope

Why

No billing = no business. App Store listing (M6 in shoploop-shopify) cannot ship without configured pricing. Decision Gate is "ships in ≤2 weeks solo" — Stripe + Shopify Billing API is genuinely a 1-week solo build.

Acceptance criteria

• Three Stripe products live with usage meters configured
• Test merchant subscribes, gets over-cap upsell, downgrades, cancels
• Shopify Billing API parity verified for App Store install path
• Revenue dashboard surfaces MRR + tier mix in admin

Affected repos

shoploop (primary), shoploop-shopify (Shopify Billing API), shoploop-core (meter event emitter)

Cost

Stripe fees only — 2.9% + $0.30 per transaction. No fixed cost.