feat: ImageLayoutEditor, arrow-key nav, multi-select bold, wider columns

- New ImageLayoutEditor: SVG overlay on original scan with draggable
  column dividers, horizontal guidelines (margins/header/footer),
  double-click to add columns, x-button to delete
- GridTable: MIN_COL_WIDTH 40→80px for better readability
- Arrow up/down keys navigate between rows in the grid editor
- Ctrl+Click for multi-cell selection, Ctrl+B to toggle bold on selection
- getAdjacentCell works for cells that don't exist yet (new rows/cols)
- deleteColumn now merges x-boundaries correctly
- Session restore fix: grid_editor_result/structure_result in session GET
- Footer row 3-state cycle, auto-create cells for empty footer rows
- Grid save/build/GT-mark now advance current_step=11

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

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

@@ -34,6 +34,8 @@ export function GridEditor({ sessionId, onNext }: GridEditorProps) {
     getAdjacentCell,
     deleteColumn,
     addColumn,
+    deleteRow,
+    addRow,
   } = useGridEditor(sessionId)
 
   const [showOverlay, setShowOverlay] = useState(false)
@@ -163,6 +165,11 @@ export function GridEditor({ sessionId, onNext }: GridEditorProps) {
             +{grid.summary.recovered_colored} recovered
           </span>
         )}
+        {grid.dictionary_detection?.is_dictionary && (
+          <span className="px-1.5 py-0.5 rounded bg-blue-50 dark:bg-blue-900/20 text-blue-600 dark:text-blue-400 border border-blue-200 dark:border-blue-800">
+            Woerterbuch ({Math.round(grid.dictionary_detection.confidence * 100)}%)
+          </span>
+        )}
         <span className="text-gray-400">
           {grid.duration_seconds.toFixed(1)}s
         </span>
@@ -223,6 +230,8 @@ export function GridEditor({ sessionId, onNext }: GridEditorProps) {
                   onNavigate={handleNavigate}
                   onDeleteColumn={deleteColumn}
                   onAddColumn={addColumn}
+                  onDeleteRow={deleteRow}
+                  onAddRow={addRow}
                 />
               </div>
             ) : (