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/backup/volume.py

@@ -13,7 +13,9 @@ def get_storage_path(volume_name: str) -> str:
     return f"{path}/"
 
 
-def get_last_backup_dir(versions_dir: str, volume_name: str, current_backup_dir: str) -> str | None:
+def get_last_backup_dir(
+    versions_dir: str, volume_name: str, current_backup_dir: str
+) -> str | None:
     versions = sorted(os.listdir(versions_dir), reverse=True)
     for version in versions:
         candidate = os.path.join(versions_dir, version, volume_name, "files", "")
@@ -37,6 +39,8 @@ def backup_volume(versions_dir: str, volume_name: str, volume_dir: str) -> None:
         execute_shell_command(cmd)
     except BackupException as e:
         if "file has vanished" in str(e):
-            print("Warning: Some files vanished before transfer. Continuing.", flush=True)
+            print(
+                "Warning: Some files vanished before transfer. Continuing.", flush=True
+            )
         else:
             raise