feat(email): per-variant paid/unpaid body templates in settings

The previous single body field could not distinguish 'use the default' from
'save the pre-filled default', so the first settings save locked the hint in
as a custom override for ALL orders — the paid/unpaid default logic never ran.

Give each payment state its own editable body field (emailBodyHtmlDePaid /
emailBodyHtmlEnPaid) with its own empty-fallback. A body submitted unchanged
from its built-in default is stored as empty, so 'use default' survives saves
and future default updates propagate.

.vscode/settings.json

@@ -2,6 +2,8 @@
     "chat.tools.terminal.autoApprove": {
         "setopt": true,
         "npx shopify": true,
-        "npx tsx": true
+        "npx tsx": true,
+        "./update_dev_system.sh": true,
+        "./show_dev_logs.sh": true
     }
 }