Extract page number as metadata instead of silently removing it

_filter_footer_words now returns page number info (text, y_pct, number)
instead of just removing footer words. The page number is included in
the grid result as `page_number` and displayed in the frontend summary
bar as "S. 233".

This preserves page numbers for later page concatenation in the
customer frontend while still removing them from the grid content.

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

admin-lehrer/components/grid-editor/GridEditor.tsx

@@ -174,6 +174,11 @@ export function GridEditor({ sessionId, onNext }: GridEditorProps) {
             Woerterbuch ({Math.round(grid.dictionary_detection.confidence * 100)}%)
           </span>
         )}
+        {grid.page_number?.text && (
+          <span className="px-1.5 py-0.5 rounded bg-gray-100 dark:bg-gray-700 text-gray-600 dark:text-gray-300 border border-gray-200 dark:border-gray-600">
+            S. {grid.page_number.text}
+          </span>
+        )}
         <span className="text-gray-400">
           {grid.duration_seconds.toFixed(1)}s
         </span>

admin-lehrer/components/grid-editor/types.ts

@@ -20,6 +20,13 @@ export interface DictionaryDetection {
   headword_col_index: number | null
 }
 
+/** Page number extracted from footer region of the scan. */
+export interface PageNumber {
+  text: string
+  y_pct: number
+  number?: number
+}
+
 /** A complete structured grid with zones, ready for the Excel-like editor. */
 export interface StructuredGrid {
   session_id: string
@@ -31,6 +38,7 @@ export interface StructuredGrid {
   formatting: GridFormatting
   layout_metrics?: LayoutMetrics
   dictionary_detection?: DictionaryDetection
+  page_number?: PageNumber | null
   duration_seconds: number
   edited?: boolean
   layout_dividers?: LayoutDividers