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/orientation_crop_api.py

@@ -174,7 +174,8 @@ async def auto_crop(session_id: str):
     cached = await _ensure_cached(session_id)
 
     # Use oriented image if available, else original
-    img_bgr = cached.get("oriented_bgr") or cached.get("original_bgr")
+    oriented = cached.get("oriented_bgr")
+    img_bgr = oriented if oriented is not None else cached.get("original_bgr")
     if img_bgr is None:
         raise HTTPException(status_code=400, detail="No image available for cropping")
 
@@ -236,7 +237,8 @@ async def manual_crop(session_id: str, req: ManualCropRequest):
     """Manually crop using percentage coordinates."""
     cached = await _ensure_cached(session_id)
 
-    img_bgr = cached.get("oriented_bgr") or cached.get("original_bgr")
+    oriented = cached.get("oriented_bgr")
+    img_bgr = oriented if oriented is not None else cached.get("original_bgr")
     if img_bgr is None:
         raise HTTPException(status_code=400, detail="No image available for cropping")
 
@@ -294,7 +296,8 @@ async def skip_crop(session_id: str):
     """Skip cropping — use oriented (or original) image as-is."""
     cached = await _ensure_cached(session_id)
 
-    img_bgr = cached.get("oriented_bgr") or cached.get("original_bgr")
+    oriented = cached.get("oriented_bgr")
+    img_bgr = oriented if oriented is not None else cached.get("original_bgr")
     if img_bgr is None:
         raise HTTPException(status_code=400, detail="No image available")