Show detected page number in session header

Extracts page_number from grid_editor_result when opening a session
and displays it as "S. 233" badge in the SessionHeader, next to the
category and GT badges.

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

admin-lehrer/components/ocr-kombi/SessionHeader.tsx

@@ -7,6 +7,7 @@ interface SessionHeaderProps {
   sessionName: string
   activeCategory?: DocumentCategory
   isGroundTruth: boolean
+  pageNumber?: number | null
   onUpdateCategory: (category: DocumentCategory) => void
 }
 
@@ -14,6 +15,7 @@ export function SessionHeader({
   sessionName,
   activeCategory,
   isGroundTruth,
+  pageNumber,
   onUpdateCategory,
 }: SessionHeaderProps) {
   const [showCategoryPicker, setShowCategoryPicker] = useState(false)
@@ -36,6 +38,11 @@ export function SessionHeader({
       >
         {catInfo ? `${catInfo.icon} ${catInfo.label}` : 'Kategorie setzen'}
       </button>
+      {pageNumber != null && (
+        <span className="text-xs px-2 py-0.5 rounded-full bg-gray-100 dark:bg-gray-700 border border-gray-200 dark:border-gray-600 text-gray-600 dark:text-gray-300">
+          S. {pageNumber}
+        </span>
+      )}
       {isGroundTruth && (
         <span className="text-xs px-2 py-0.5 rounded-full bg-amber-50 dark:bg-amber-900/20 border border-amber-300 dark:border-amber-700 text-amber-700 dark:text-amber-300">
           GT