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/zeugnis/worker.py

@@ -83,7 +83,7 @@ class ZeugnisCrawler:
 
         # Initialize database connection
         try:
-            from metrics_db import get_pool
+            from metrics.db import get_pool
             self.db_pool = await get_pool()
         except Exception as e:
             print(f"Failed to get database pool: {e}")