Restructure: Move 43 files into 8 domain packages (backend-lehrer)

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

backend-lehrer/correction_api.py

@@ -1,23 +1,4 @@
-"""
-Correction API - REST API fuer Klassenarbeits-Korrektur.
-
-Barrel re-export: router and all public symbols.
-"""
-
-from correction_endpoints import router  # noqa: F401
-from correction_models import (  # noqa: F401
-    CorrectionStatus,
-    AnswerEvaluation,
-    CorrectionCreate,
-    CorrectionUpdate,
-    Correction,
-    CorrectionResponse,
-    OCRResponse,
-    AnalysisResponse,
-)
-from correction_helpers import (  # noqa: F401
-    corrections_store,
-    calculate_grade,
-    generate_ai_feedback,
-    process_ocr,
-)
+# Backward-compat shim -- module moved to correction/api.py
+import importlib as _importlib
+import sys as _sys
+_sys.modules[__name__] = _importlib.import_module("correction.api")