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/metrics_db.py

@@ -1,36 +1,4 @@
-"""
-PostgreSQL Metrics Database Service — Barrel Re-export
-
-Split into:
-- metrics_db_core.py     — Pool, feedback, metrics, relevance
-- metrics_db_schema.py   — Table initialization (DDL)
-- metrics_db_zeugnis.py  — Zeugnis source/document/stats operations
-
-All public names are re-exported here for backward compatibility.
-"""
-
-# Schema: table initialization
-from metrics_db_schema import init_metrics_tables  # noqa: F401
-
-# Core: pool, feedback, search logs, metrics, relevance
-from metrics_db_core import (  # noqa: F401
-    DATABASE_URL,
-    get_pool,
-    store_feedback,
-    log_search,
-    log_upload,
-    calculate_metrics,
-    get_recent_feedback,
-    get_upload_history,
-    store_relevance_judgment,
-    calculate_precision_recall,
-)
-
-# Zeugnis operations
-from metrics_db_zeugnis import (  # noqa: F401
-    get_zeugnis_sources,
-    upsert_zeugnis_source,
-    get_zeugnis_documents,
-    get_zeugnis_stats,
-    log_zeugnis_event,
-)
+# Backward-compat shim -- module moved to metrics/db.py
+import importlib as _importlib
+import sys as _sys
+_sys.modules[__name__] = _importlib.import_module("metrics.db")