Implements plans/STRIPE_PLAN.md sections 1-9 for solo Pro/Family
billing (family multi-user sharing, section 1a, deliberately deferred
-- flagged in that plan as the most novel/error-prone piece).
Decisions locked in: cancel/downgrade at period end (Stripe Portal
default), no trial period.
- lib/stripe.ts: single client factory reading STRIPE_SECRET_KEY via
site-settings (DB overrides env, same pattern as every other
provider key in this codebase).
- Webhook route rewritten on the real `stripe` SDK
(stripe.webhooks.constructEvent replaces the hand-rolled HMAC
verifier) and now handles the full event set: checkout.session.completed,
customer.subscription.{updated,deleted}, invoice.{payment_failed,paid}.
past_due deliberately never downgrades tier on its own -- Stripe
retries the card first, recovering via invoice.paid or eventually
giving up via subscription.deleted. Every handler audit-logs under
billing.<event>. Dedup via the existing processed_stripe_events
table, unchanged.
- Schema: tierDefinitions gained stripe{ProductId,PriceIdMonthly,
PriceIdYearly} (the lookup table mapping a Price back to a tier on
checkout); users gained stripeSubscriptionId/subscriptionStatus/
currentPeriodEnd.
- New POST /api/v1/billing/checkout (creates a subscription Checkout
Session, allow_promotion_codes: true), POST /api/v1/billing/portal
(Stripe's hosted self-serve cancel/upgrade/card-update), GET
/api/v1/billing/status.
- /settings/billing: current plan + renewal date, past_due warning,
usage-vs-limits (reuses the existing UsageQuotaSection), plan
comparison cards with per-tier Checkout buttons, manage-billing
button once a Stripe customer exists.
- /admin/billing: connection status (test/live mode detection),
subscriber counts, past-due list, recent billing audit events, link
to Stripe Dashboard. Tier Limits page extended with the three Stripe
price fields per tier (own render branch, not the numeric+Unlimited-
switch machinery the existing fields use).
Before going live: an admin needs to create real Products/Prices in
Stripe, enter the IDs on Tier Limits, and configure the Stripe-side
webhook endpoint -- all operational steps the plan always called for,
none of it code.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Arnaud