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>

klausur-service/backend/ocr_pipeline_sessions.py

@@ -178,6 +178,18 @@ async def get_session_info(session_id: str):
         result["word_result"] = session["word_result"]
     if session.get("doc_type_result"):
         result["doc_type_result"] = session["doc_type_result"]
+    if session.get("structure_result"):
+        result["structure_result"] = session["structure_result"]
+    if session.get("grid_editor_result"):
+        # Include summary only to keep response small
+        gr = session["grid_editor_result"]
+        result["grid_editor_result"] = {
+            "summary": gr.get("summary", {}),
+            "zones_count": len(gr.get("zones", [])),
+            "edited": gr.get("edited", False),
+        }
+    if session.get("ground_truth"):
+        result["ground_truth"] = session["ground_truth"]
 
     # Sub-session info
     if session.get("parent_session_id"):