Persist paymentStatus on the Invoice at generation time and use it at send
time to pick the default email body. Paid orders (paid/refunded/voided) now
get a body without the bank-transfer reference hint; outstanding orders keep
it. Custom merchant templates still override the defaults for both cases.
- Add Invoice.paymentStatus column + migration
- Split DEFAULT_EMAIL_BODY_{DE,EN} into _PAID/_UNPAID variants
- Persist paymentStatus in generateInvoice; select default in email.server
- Document behaviour on the settings page
- Add email-templates test (paid omits hint, unpaid keeps it)
Mirrors the layout from data/mail_template.png:
- Company name + greeting headline
- Body referencing the invoice number
- Inline logo (cid:invoice-logo) attached automatically
- Footer with mailto + website links
New template vars: {{shopEmail}}, {{shopWebsite}}.
Settings UI prefills empty fields with the defaults so users see and
can tweak them without losing the fallback.
Gerhard Scheikl