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/admin/__init__.py

@@ -2,5 +2,5 @@
 admin package — admin APIs for NiBiS, RAG, templates.
 
 Backward-compatible re-exports: consumers can still use
-``from admin_api import ...`` etc. via the shim files in backend/.
+``from admin.api import ...`` etc. via the shim files in backend/.
 """

klausur-service/backend/admin/api.py

@@ -7,7 +7,7 @@ This module was split into:
   - admin_templates.py  (Legal templates ingestion, search)
 
 The `router` object is assembled here by including all sub-routers.
-Importers that did `from admin_api import router` continue to work.
+Importers that did `from admin.api import router` continue to work.
 """
 
 from fastapi import APIRouter

klausur-service/backend/admin/rag.py

@@ -28,7 +28,7 @@ except ImportError:
     MINIO_AVAILABLE = False
 
 try:
-    from metrics_db import (
+    from metrics.db import (
         init_metrics_tables, store_feedback, log_search, log_upload,
         calculate_metrics, get_recent_feedback, get_upload_history
     )