Lohnt sich dein eigenes Systeme.io?

Build a self-hosted, single-operator funnel and course platform. One person runs it, no multi-tenancy.

Stack, no substitutions:
- Next.js 15, App Router, TypeScript, Tailwind
- SQLite via better-sqlite3, single file at ./data/app.db, migrations as plain SQL in ./migrations
- Stripe Checkout plus webhooks for payments
- Resend for outbound email
- No auth provider: magic-link email login for buyers, single admin password from .env

What to build:
1. Funnel pages defined as MDX files in ./content/pages. Each has frontmatter: slug, title, headline, subhead, cta, optional priceId. Render server-side with a clean default layout.
2. Opt-in form component posting to /api/optin. Store contacts in SQLite: email, name, tags, source page, created_at, unsubscribed_at. Double opt-in optional via env flag.
3. Email engine: broadcasts and sequences. A sequence is a JSON file in ./content/sequences with steps (delay in hours, subject, MDX body). A worker script (npm run worker) runs every minute via node-cron, sends due steps through Resend, logs every send in an email_events table. Every email gets a one-click unsubscribe link with a signed token, and List-Unsubscribe headers.
4. Checkout: /api/checkout creates a Stripe Checkout Session for a given priceId. Webhook handler grants a course entitlement on checkout.session.completed, and revokes on refund.
5. Course area at /learn: modules and lessons from MDX in ./content/course, gated by entitlement, video via an embed URL field. Track lesson completion per contact.
6. Affiliate tracking: /r/CODE sets a 60 day first-party cookie, attributes the sale on webhook, writes rows to a commissions table with status pending. Admin page lists commissions. No payouts.
7. Admin at /admin behind the env password: contacts list with search, broadcast composer with a test-send, sales list, commissions list, CSV export of contacts and sales.

Out of scope, do not build: drag-and-drop editors, webinars, blog CMS, tax handling, affiliate payouts, IP warmup, analytics beyond page-view counts stored locally.

Rules: all secrets in .env (STRIPE_SECRET_KEY, STRIPE_WEBHOOK_SECRET, RESEND_API_KEY, ADMIN_PASSWORD, APP_URL). No telemetry, no external analytics. Seed the database with two demo contacts, one demo course and one demo sequence so npm run dev shows a working funnel immediately. Include a README with setup steps, a Stripe CLI webhook command, and a deploy note for a single VPS with a persistent volume.