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

tests/unit/test_backup.py

@@ -6,7 +6,9 @@ from baudolo.backup.app import requires_stop
 
 class TestRequiresStop(unittest.TestCase):
     @patch("baudolo.backup.app.get_image_info")
-    def test_requires_stop_false_when_all_images_are_whitelisted(self, mock_get_image_info):
+    def test_requires_stop_false_when_all_images_are_whitelisted(
+        self, mock_get_image_info
+    ):
         # All containers use images containing allowed substrings
         mock_get_image_info.side_effect = [
             "repo/mastodon:v4",
@@ -17,7 +19,9 @@ class TestRequiresStop(unittest.TestCase):
         self.assertFalse(requires_stop(containers, whitelist))
 
     @patch("baudolo.backup.app.get_image_info")
-    def test_requires_stop_true_when_any_image_is_not_whitelisted(self, mock_get_image_info):
+    def test_requires_stop_true_when_any_image_is_not_whitelisted(
+        self, mock_get_image_info
+    ):
         mock_get_image_info.side_effect = [
             "repo/mastodon:v4",
             "repo/nginx:latest",