Restructure: Move ocr_pipeline + labeling + crop into ocr/ package

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

klausur-service/backend/ocr/pipeline/overlays.py

@@ -0,0 +1,34 @@
+"""
+Overlay image rendering for OCR pipeline — barrel re-export.
+
+All implementation split into:
+  ocr_pipeline_overlay_structure — structure overlay (boxes, zones, colors, graphics)
+  ocr_pipeline_overlay_grid     — columns, rows, words overlays
+
+Lizenz: Apache 2.0
+DATENSCHUTZ: Alle Verarbeitung erfolgt lokal.
+"""
+
+from fastapi import HTTPException
+from fastapi.responses import Response
+
+from .overlay_structure import _get_structure_overlay  # noqa: F401
+from .overlay_grid import (  # noqa: F401
+    _get_columns_overlay,
+    _get_rows_overlay,
+    _get_words_overlay,
+)
+
+
+async def render_overlay(overlay_type: str, session_id: str) -> Response:
+    """Dispatch to the appropriate overlay renderer."""
+    if overlay_type == "structure":
+        return await _get_structure_overlay(session_id)
+    elif overlay_type == "columns":
+        return await _get_columns_overlay(session_id)
+    elif overlay_type == "rows":
+        return await _get_rows_overlay(session_id)
+    elif overlay_type == "words":
+        return await _get_words_overlay(session_id)
+    else:
+        raise HTTPException(status_code=400, detail=f"Unknown overlay type: {overlay_type}")