refactor: use de gruyter ci

frontend/src/routes/documents/[id]/edit/+page.svelte

@@ -42,9 +42,7 @@
     <!-- Heading -->
     <div class="mb-6">
         <a href="/documents/{doc.id}" class="inline-flex items-center text-xs font-bold uppercase tracking-widest text-gray-500 hover:text-brand-navy transition-colors group mb-4">
-            <svg class="w-4 h-4 mr-2 transform group-hover:-translate-x-1 transition-transform" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-                <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M10 19l-7-7m0 0l7-7m-7 7h18"/>
-            </svg>
+            <img src="/degruyter-icons/Simple/Medium-24px/SVG/Action/Arrow/Arrow-Left-MD.svg" alt="" aria-hidden="true" class="w-4 h-4 mr-2 transform group-hover:-translate-x-1 transition-transform" />
             Zurück zum Dokument
         </a>
         <h1 class="text-3xl font-serif text-brand-navy">
@@ -189,9 +187,7 @@
             <h2 class="text-xs font-bold uppercase tracking-widest text-gray-400 mb-5">Datei</h2>
 
             <div class="flex items-center gap-3 mb-4 text-sm text-gray-600 bg-brand-sand/20 rounded px-3 py-2">
-                <svg class="w-4 h-4 text-brand-navy flex-shrink-0" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M9 12h6m-6 4h6m2 5H7a2 2 0 01-2-2V5a2 2 0 012-2h5.586a1 1 0 01.707.293l5.414 5.414a1 1 0 01.293.707V19a2 2 0 01-2 2z"/>
-                </svg>
+                <img src="/degruyter-icons/Simple/Medium-24px/SVG/Action/PDF-Document-MD.svg" alt="" aria-hidden="true" class="w-4 h-4 flex-shrink-0" />
                 <span>Aktuelle Datei: <strong class="text-brand-navy font-medium">{doc.originalFilename}</strong></span>
             </div>