Wire targeted toast notifications to document status transitions

Adds emit_notification_user() to 7 endpoints so the acting user and
all admins/owners receive a real-time toast on key document actions:
confirm/cancel order, issue/void invoice, confirm return, confirm PO,
receive PO goods. Other staff and viewers are not notified.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/order/api/engine/issue_invoice.php

@@ -28,6 +28,8 @@
 
         $answer['success'] = 1;
         $answer['message'] = 'Invoice issued.';
+        require_once '../../../assets/utils/notify_node.php';
+        emit_notification_user($company_id, $user_id, 'Invoice Issued', 'The invoice has been issued.', 'success');
 
         // Auto-post GL for this document
         $sth = $pdo2->prepare("SELECT doc_type, formula_id FROM td_invoice WHERE company_id = :cid AND id = :id LIMIT 1");