fix: UnboundLocalError edge_tolerance in Step 5c

Variable wurde vor ihrer Definition in Step 7 referenziert.
Eigene margin_thresh Variable fuer Step 5c eingefuehrt.

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

klausur-service/backend/cv_layout.py

@@ -1274,17 +1274,15 @@ def detect_column_geometry(ocr_img: np.ndarray, dewarped_bgr: np.ndarray) -> Opt
     if len(validated_gaps) > 2:
         edge_tolerance_align = max(8, content_w // 150)
         min_aligned_ratio = 0.25  # at least 25% of words must share a left-edge bin
-
-        margin_left_end = edge_tolerance if validated_gaps and validated_gaps[0][0] <= max(10, int(content_w * 0.02)) else -1
-        margin_right_start = content_w - max(10, int(content_w * 0.02))
+        margin_thresh = max(10, int(content_w * 0.02))
 
         alignment_validated = []
         for gap_start_rel, gap_end_rel in validated_gaps:
             # Skip margin gaps — they don't need alignment validation
-            if gap_start_rel <= max(10, int(content_w * 0.02)):
+            if gap_start_rel <= margin_thresh:
                 alignment_validated.append((gap_start_rel, gap_end_rel))
                 continue
-            if gap_end_rel >= margin_right_start:
+            if gap_end_rel >= content_w - margin_thresh:
                 alignment_validated.append((gap_start_rel, gap_end_rel))
                 continue