fix: numpy array or-Verknuepfung in Crop/Deskew + ImageCompareView Labels

- orientation_crop_api.py: `array or array` durch `is not None` ersetzt
  (ValueError bei numpy Arrays)
- ocr_pipeline_api.py: gleicher Fix fuer Deskew-Fallback-Kette
- ImageCompareView.tsx: Fallback-Text nutzt rightLabel statt "Begradigung"

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

klausur-service/backend/ocr_pipeline_api.py

@@ -484,7 +484,8 @@ async def auto_deskew(session_id: str):
     cached = _get_cached(session_id)
 
     # Use cropped image as input (from step 2), fall back to oriented, then original
-    img_bgr = cached.get("cropped_bgr") or cached.get("oriented_bgr") or cached.get("original_bgr")
+    img_bgr = next((v for k in ("cropped_bgr", "oriented_bgr", "original_bgr")
+                     if (v := cached.get(k)) is not None), None)
     if img_bgr is None:
         raise HTTPException(status_code=400, detail="No image available for deskewing")
 
@@ -589,7 +590,8 @@ async def manual_deskew(session_id: str, req: ManualDeskewRequest):
         await _load_session_to_cache(session_id)
     cached = _get_cached(session_id)
 
-    img_bgr = cached.get("cropped_bgr") or cached.get("oriented_bgr") or cached.get("original_bgr")
+    img_bgr = next((v for k in ("cropped_bgr", "oriented_bgr", "original_bgr")
+                     if (v := cached.get(k)) is not None), None)
     if img_bgr is None:
         raise HTTPException(status_code=400, detail="No image available for deskewing")