Restructure: Move 52 files into 7 domain packages

korrektur/ zeugnis/ admin/ compliance/ worksheet/ training/ metrics/
52 shims, relative imports, RAG untouched.

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

klausur-service/backend/training/api.py

@@ -0,0 +1,31 @@
+"""
+Training API — barrel re-export.
+
+The actual code lives in:
+  - training_models.py      (enums, Pydantic models, in-memory state)
+  - training_simulation.py  (simulate_training_progress, SSE generators)
+  - training_routes.py      (FastAPI router + all endpoints)
+"""
+
+# Models & enums
+from .models import (  # noqa: F401
+    TrainingStatus,
+    ModelType,
+    TrainingConfig,
+    TrainingMetrics,
+    TrainingJob,
+    ModelVersion,
+    DatasetStats,
+    TrainingState,
+    _state,
+)
+
+# Simulation helpers
+from .simulation import (  # noqa: F401
+    simulate_training_progress,
+    training_metrics_generator,
+    batch_ocr_progress_generator,
+)
+
+# Router
+from .routes import router  # noqa: F401