Lohnt sich dein eigenes Sendcore?

Build me a private Shopify campaign sender for one store I already own. Not a SaaS, not multi-tenant, no signup. Requirements:

- Node 22 + Fastify + better-sqlite3, server-rendered HTML, no client framework.
- Read the store with a Shopify custom app Admin API token I create myself
  (read_products, read_customers, read_orders); no OAuth, no App Store install flow.
- Send through one bulk email provider with my API key and my already-authenticated
  sending domain; both in .env, ship a .env.example.
- SQLite tables: contacts (email, consent state, source, created_at), products cached
  from Shopify, campaigns (subject, body_html, status, sent_at), and sends
  (contact_id, campaign_id, status, error).
- Every contact carries an explicit consent state. Never send to an unsubscribed or
  unconsented contact, and prove that with a test.
- Every email gets a working one-click unsubscribe link plus List-Unsubscribe
  headers, backed by a signed token and honoured immediately.
- The composer is a plain HTML textarea plus a product picker that inserts image,
  title, price, and link from the synced cache. Render with inline styles and a
  table layout so it survives Gmail and Outlook; no external stylesheets or web fonts.
- Always send a test to myself first, and require a typed confirmation of the
  recipient count before any real send.
- Send in batches with retry and backoff, one send row per recipient, so a crash
  resumes instead of double-sending. Report delivered and failed from the sends
  table only; do not invent open or click tracking.
- CSV import and export for contacts so the data is never trapped in the app.
- Tests: the consent gate, the unsubscribe token, batch resume, and one end-to-end
  campaign against a mocked provider.
- README states what this is not: no deliverability operations, no bounce or
  complaint processing, no App Store distribution, no billing. Say plainly that real
  volume from a cold domain lands in spam, and warmup is now the reader's job.