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>

backend-lehrer/vocabulary/api.py

@@ -22,7 +22,7 @@ from .db import (
     get_all_pos,
     VocabularyWord,
 )
-from learning_units import (
+from units.learning import (
     LearningUnitCreate,
     create_learning_unit,
     get_learning_unit,
@@ -343,7 +343,7 @@ async def api_translate_words(payload: TranslateRequest):
     Uses local LLM (Ollama) for translation. Results are cached in the
     vocabulary_words.translations JSONB field.
     """
-    from translation_service import translate_and_store
+    from services.translation import translate_and_store
 
     if payload.target_language not in {"tr", "ar", "uk", "ru", "pl", "fr", "es"}:
         raise HTTPException(status_code=400, detail=f"Sprache '{payload.target_language}' nicht unterstuetzt")