SMTP per-shop configurabile dalle Impostazioni (password cifrata AES-256-GCM)

- Settings: smtpHost/Port/User/Pass(cifrata)/Secure/From. Vuoto -> provider
  default dell'app (env); compilato -> invio dal SMTP del merchant.
- crypto.server: encrypt/decrypt AES-256-GCM (chiave APP_ENCRYPTION_KEY).
- mailer: SmtpConfig + buildTransport(smtp) per-shop o env; mailFrom override.
  Sia ricevuta cliente sia notifica merchant usano lo SMTP del merchant.
- proxy: costruisce SmtpConfig (decifra pass), passa ai due invii.
- admin: nuovo tab 'Email (SMTP)'; password mai ri-mostrata (vuoto = invariata).
- Migrazione smtp_settings. APP_ENCRYPTION_KEY: dev in .env, prod = fly secret.

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

app/prisma/migrations/20260707152343_smtp_settings/migration.sql

@@ -0,0 +1,7 @@
+-- AlterTable
+ALTER TABLE "Settings" ADD COLUMN     "smtpFrom" TEXT,
+ADD COLUMN     "smtpHost" TEXT,
+ADD COLUMN     "smtpPass" TEXT,
+ADD COLUMN     "smtpPort" INTEGER,
+ADD COLUMN     "smtpSecure" BOOLEAN NOT NULL DEFAULT false,
+ADD COLUMN     "smtpUser" TEXT;