Backend: Python-Logging statt print, Diagnose in allen Fallbacks

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/logsetup.py

@@ -0,0 +1,11 @@
+"""Zentrales Logging-Setup — einmal in main.py aufrufen, bevor die App entsteht."""
+
+import logging
+import os
+
+
+def setup_logging() -> None:
+    logging.basicConfig(
+        level=os.environ.get("LOG_LEVEL", "INFO").upper(),
+        format="%(asctime)s %(levelname)s %(name)s %(message)s",
+    )