Revert "chore: bump version to 1.20.0"

This reverts commit 4658dfd. Die Version bleibt bei 1.12.0 — der
1.20.0-Bump war versehentlich.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: Xveyn

src/version.py

@@ -1 +1 @@
-VERSION = "1.20.0"
+VERSION = "1.13.0"