feat(gallery): publish notifies assigned customer accounts via the account email

Publishing a gallery with no inline customer_email but assigned customer
account(s) previously sent nothing (the dialog said "no notification"). Now the
publish route falls back to the existing customer_gallery_assigned "your
galleries" email (sent per assigned active account in their preferred language)
so registered customers learn the gallery is available. Inline-email path
(gallery_created) is unchanged.

The publish dialog now reflects this: with an inline email it notifies that
address; with only assigned accounts it says the account(s) will be notified;
with neither, the button is just "Publish" (no false notify promise). Exports
notifyCustomerOfNewAssignments; EN/DE strings added.

frontend/src/components/admin/PublishGalleryDialog.tsx

@@ -7,6 +7,8 @@ interface PublishGalleryDialogProps {
   eventName: string;
   requirePassword: boolean;
   customerEmail?: string | null;
+  /** Assigned customer accounts — notified via the account "your galleries" email when there's no inline email. */
+  assignedCustomerCount?: number;
   isPublishing: boolean;
   onConfirm: (password?: string) => void;
   onClose: () => void;
@@ -28,11 +30,15 @@ export const PublishGalleryDialog: React.FC<PublishGalleryDialogProps> = ({
   eventName,
   requirePassword,
   customerEmail,
+  assignedCustomerCount = 0,
   isPublishing,
   onConfirm,
   onClose,
 }) => {
   const { t } = useTranslation();
+  // Someone gets notified if there's an inline email OR an assigned account
+  // (the latter via the account "your galleries" email).
+  const willNotify = !!customerEmail || assignedCustomerCount > 0;
   const [password, setPassword] = useState('');
   const [showPassword, setShowPassword] = useState(false);
   const [error, setError] = useState<string | undefined>(undefined);
@@ -72,11 +78,18 @@ export const PublishGalleryDialog: React.FC<PublishGalleryDialogProps> = ({
                 defaultValue:
                   'Publishing "{{eventName}}" makes the gallery accessible and sends the notification email to {{customerEmail}}.',
               })
-            : t('events.publishDialog.descriptionNoEmail', {
-                eventName,
-                defaultValue:
-                  'Publishing "{{eventName}}" makes the gallery accessible. No customer email is set, so no notification will be sent.',
-              })}
+            : assignedCustomerCount > 0
+              ? t('events.publishDialog.descriptionAssignedAccount', {
+                  eventName,
+                  count: assignedCustomerCount,
+                  defaultValue:
+                    'Publishing "{{eventName}}" makes the gallery accessible. The assigned customer account(s) will be notified by email (in their language) that it is available.',
+                })
+              : t('events.publishDialog.descriptionNoEmail', {
+                  eventName,
+                  defaultValue:
+                    'Publishing "{{eventName}}" makes the gallery accessible. No customer email is set, so no notification will be sent.',
+                })}
         </p>
 
         {requirePassword && customerEmail && (
@@ -124,10 +137,10 @@ export const PublishGalleryDialog: React.FC<PublishGalleryDialogProps> = ({
             onClick={handleSubmit}
             disabled={isPublishing}
             isLoading={isPublishing}
-            leftIcon={<Send className="w-4 h-4" />}
+            leftIcon={willNotify ? <Send className="w-4 h-4" /> : undefined}
             className="flex-1"
           >
-            {t('events.publishAndNotify')}
+            {willNotify ? t('events.publishAndNotify') : t('events.publishDialog.justPublish', 'Publish')}
           </Button>
         </div>
       </Card>