Make customer upload-confirmation email opt-out via settings

New smtp_notify_customer toggle in the SMTP section. Defaults to true
to preserve existing behavior. When unchecked, customers no longer
receive the upload summary even if they have an email on file; staff
and (optionally) admins keep getting their notifications.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server.js

@@ -272,6 +272,7 @@ api.get('/settings', auth.requireAdmin, (req, res) => {
     smtp_pass_set: !!settings.get('smtp_pass', ''),
     smtp_from: settings.get('smtp_from', ''),
     smtp_notify_admin: settings.get('smtp_notify_admin', 'false') === 'true',
+    smtp_notify_customer: settings.get('smtp_notify_customer', 'true') === 'true',
   });
 });
 
@@ -301,6 +302,8 @@ api.put('/settings', auth.requireAdmin, (req, res) => {
   if (b.smtp_from !== undefined)  settings.set('smtp_from', String(b.smtp_from || '').trim());
   if (b.smtp_notify_admin !== undefined)
     settings.set('smtp_notify_admin', b.smtp_notify_admin ? 'true' : 'false');
+  if (b.smtp_notify_customer !== undefined)
+    settings.set('smtp_notify_customer', b.smtp_notify_customer ? 'true' : 'false');
   res.json({ ok: true });
 });
 

src/upload-notifier.js

@@ -15,7 +15,8 @@ function fmtSize(n) {
 
 function recipientsFor(customer) {
   const out = [];
-  if (customer.email) out.push({ kind: 'customer', to: customer.email });
+  const notifyCustomer = settings.get('smtp_notify_customer', 'true') === 'true';
+  if (notifyCustomer && customer.email) out.push({ kind: 'customer', to: customer.email });
 
   // Staff assigned to this customer (with email)
   const staff = db.prepare(`