feat(helpdesk): add handover protocol schema editor to software products

Add a JSON-based schema editor as a new tab on the software product edit
page. Admins can define protocol fields (heading, paragraph, text,
textarea, number, date, checkbox, select) via a structured UI with
add/remove/reorder controls. The schema is stored as a versioned JSON
column on the product row.

Includes DB migration, server-side validation (type whitelist, key
uniqueness, key format, max 50 fields, select option checks), i18n
(DE+EN), CSS, and 10 PHPUnit tests.

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

modules/helpdesk/lib/Module/Helpdesk/Repository/SoftwareProductRepository.php

@@ -92,6 +92,21 @@ class SoftwareProductRepository
         ];
     }
 
+    public function updateHandoverSchema(string $code, ?string $schemaJson): bool
+    {
+        if (trim($code) === '') {
+            return false;
+        }
+
+        $result = DB::update(
+            'UPDATE helpdesk_software_products SET handover_protocol_schema = ? WHERE code = ?',
+            $schemaJson,
+            $code
+        );
+
+        return $result !== false;
+    }
+
     public function updateName(string $code, string $name): bool
     {
         if (trim($code) === '') {