MVP core recesso: App Proxy flow + ricevuta durevole + design storefront

- A1: SPEC-MVP-RECESSO.md (criteri + copy IT)
- A3: App Proxy /apps/recesso — lookup guest ordine+email (anti-leak), form 2-step,
  funzione dedicata Conferma recesso, persist WithdrawalRequest + transmittedAt + AuditLog
- A4: ricevuta durevole via nodemailer (mailer.server.ts) + receiptSentAt + AuditLog
- Design: recesso.server.ts restyle token CSS light/dark, coerente Shopify
- Fix: @shopify/shopify-api pinnato 13.1.0 (dedupe) -> tsc clean
- PLAN: A5 esteso a motore di stile a 3 livelli

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Mv83a29B4eFv5ixoj6PoE1

app/.env.example

@@ -13,3 +13,13 @@ SHOPIFY_APP_URL=https://your-tunnel-or-fly-url.example
 
 # Postgres connection string (Fly Postgres or Supabase).
 DATABASE_URL=postgresql://user:password@host:5432/recesso?sslmode=require
+
+# Email ricevuta recesso (supporto durevole).
+# DEV: Mailpit → SMTP_HOST=localhost SMTP_PORT=1025 SMTP_SECURE=false (nessuna auth).
+# PROD: provider reale (Resend/Postmark/SMTP) con SMTP_USER/SMTP_PASS.
+SMTP_HOST=smtp.your-provider.example
+SMTP_PORT=587
+SMTP_SECURE=false
+SMTP_USER=your_smtp_user
+SMTP_PASS=your_smtp_password
+MAIL_FROM=Recesso <no-reply@yourdomain.example>