fix(backup): log missing db config instead of raising

- Use module logger in backup/db.py
- Skip db dump when no databases.csv entry is present
- Apply black/formatting cleanup across backup/restore/tests

https://chatgpt.com/share/69519d45-b0dc-800f-acb6-6fb8504e9b46

src/baudolo/restore/db/__init__.py

@@ -1 +1 @@
-"""Database restore handlers (Postgres, MariaDB/MySQL)."""
+"""Database restore handlers (Postgres, MariaDB/MySQL)."""