Newsletter with paid tiers

Build a newsletter platform (Substack-lite).

Core features:
1. Writer publishes posts (markdown/rich text) with cover images
2. Public archive + RSS
3. Free and paid subscriptions via Stripe
4. Email each new post to subscribers (Resend), track open rate
5. Writer dashboard: MRR, subscribers, top posts

Data: posts, subscribers, subscriptions, sends.
Must-haves: paywall on paid posts, unsubscribe compliance, custom domain.