Fix: Update all old-style imports inside packages to new paths

65 files in klausur-service packages + 3 in backend-lehrer packages
had stale imports referencing deleted shim modules.

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

klausur-service/backend/ocr/review/spell.py

@@ -219,7 +219,7 @@ def spell_review_entries_sync(entries: List[Dict]) -> Dict:
     # Use SmartSpellChecker if available
     _smart = None
     try:
-        from smart_spell import SmartSpellChecker
+        from ocr.spell.smart_spell import SmartSpellChecker
         _smart = SmartSpellChecker()
         logger.debug("spell_review: using SmartSpellChecker")
     except Exception: