Fix: Resolve all lint errors from ocr/ restructure

- Added ocr_region import to cell_grid/build.py and legacy.py
- Fixed circular import in engines.py via lazy import
- Auto-fixed 22 unused imports via ruff --fix

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

klausur-service/backend/ocr/detect/box_layout.py

@@ -10,7 +10,7 @@ Used by the Box-Grid-Review step to rebuild box zones with correct structure.
 import logging
 import re
 import statistics
-from typing import Any, Dict, List, Optional, Tuple
+from typing import Any, Dict, List, Optional
 
 logger = logging.getLogger(__name__)
 
@@ -149,7 +149,7 @@ def build_box_zone_grid(
 
     Returns the same format as _build_zone_grid (columns, rows, cells, header_rows).
     """
-    from grid_editor_helpers import _build_zone_grid, _cluster_rows
+    from grid_editor_helpers import _build_zone_grid
 
     if not zone_words:
         return {

klausur-service/backend/ocr/detect/color_detect.py

@@ -14,7 +14,7 @@ DATENSCHUTZ: Alle Verarbeitung erfolgt lokal.
 """
 
 import logging
-from typing import Any, Dict, List, Optional, Tuple
+from typing import Dict, List, Tuple
 
 import cv2
 import numpy as np

klausur-service/backend/ocr/detect/syllable/core.py

@@ -9,7 +9,7 @@ DATENSCHUTZ: Alle Verarbeitung erfolgt lokal.
 
 import logging
 import re
-from typing import Any, Dict, List, Optional, Tuple
+from typing import Dict, List, Optional
 
 logger = logging.getLogger(__name__)
 

klausur-service/backend/ocr/detect/syllable/merge.py

@@ -9,7 +9,7 @@ DATENSCHUTZ: Alle Verarbeitung erfolgt lokal.
 
 import logging
 import re
-from typing import Any, Dict, List, Optional
+from typing import Dict, List, Optional
 
 import numpy as np