Should you build your own Sellfy?

Build a personal replacement for Sellfy in an empty repository.
Use Next.js 15, TypeScript, PostgreSQL, Drizzle ORM, Stripe Checkout, and S3-compatible storage; do not offer alternative stacks.
The core loop is: sell a small catalog of digital files and simple subscriptions from a user-owned storefront, deliver purchased files, and manage customers.
Make the first run work locally with one documented command.
Store all user data locally by default and make export straightforward.
Put secrets in .env, ship .env.example, and never commit credentials.
Implement products, variants, prices, files or lessons, coupons, customers, orders, and entitlements.
Use Stripe-hosted Checkout and verify every webhook signature and idempotency key.
Grant access only after confirmed payment and revoke it on refund or chargeback.
Create a customer library with signed short-lived download or lesson URLs.
Add order search, resend receipt, refund handoff, export, and an immutable event log.
Document taxes as the creator's responsibility and do not calculate unsupported jurisdictions.
Include clear empty, loading, success, and recoverable error states.
Add input validation, safe filenames, and graceful handling of unavailable APIs.
Write focused tests for the core transformation and one end-to-end happy path.
Create a README with setup, architecture, permissions, data location, and backup steps.
Do not add accounts, billing, telemetry, analytics, or a hosted control plane.
Deliberately leave out merchant-of-record tax remittance.
Deliberately leave out a buyer marketplace or affiliate network.
Deliberately leave out advanced communities, certificates, mobile apps, and enterprise learning features.
Finish by running the tests and listing the exact commands used.