Cleanup: Delete ALL 242 shims, update ALL consumer imports

klausur-service: 183 shims deleted, 26 test files + 8 source files updated
backend-lehrer: 59 shims deleted, main.py + 8 source files updated

All imports now use the new package paths directly.
Zero shims remaining in the entire codebase.

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

klausur-service/backend/tests/debug_shear.py

@@ -6,7 +6,7 @@ sys.path.insert(0, "/app/backend")
 import cv2
 import numpy as np
 import pytesseract
-from ocr_pipeline_session_store import get_session_db
+from ocr.pipeline.session_store import get_session_db
 
 SESSION_ID = "3dcb1897-09a6-4b80-91b5-7e4207980bf3"
 
@@ -74,7 +74,7 @@ async def main():
 
     # Also test the 4 dewarp methods directly
     print("\n--- Dewarp method results on deskewed image ---")
-    from cv_vocab_pipeline import (
+    from ocr.cv_pipeline import (
         _detect_shear_angle, _detect_shear_by_projection,
         _detect_shear_by_hough, _detect_shear_by_text_lines,
     )