style!: adopt the core lint bar and migrate to it

The package carried no ruff configuration at all, so it ran on the defaults (E4+E7+E9+F) while infinito-nexus-core, its only consumer, holds itself to a far wider selection. Measured against that selection this tree had 224 findings. It now has none.

The selector list is core's verbatim so both repositories answer to one bar. target-version stays py39 rather than core's py311, because requires-python still declares >=3.9 and pyupgrade would otherwise propose syntax the declared minimum cannot run. Every ignore carries its reason: S603/S607 in particular, since running docker and dump binaries from PATH in list form is this tool's whole job and is already injection-safe.

Two conversions are judgement rather than mechanics. os.path.join(dir, '') was the rsync idiom for a trailing separator, which Path drops, so it becomes an explicit os.sep. os.path.abspath stays where Path.resolve() would follow symlinks and let a symlinked volume test as inside the snapshot subject.

BREAKING CHANGE: VersionMismatch is renamed VersionMismatchError.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

tests/unit/backup/test_db_mariadb_dump.py

@@ -2,15 +2,13 @@ import tempfile
 import unittest
 from unittest.mock import patch
 
-import pandas
+import pandas as pd
 
 from baudolo.backup import db as db_mod
 
 
 def _df(rows):
-    return pandas.DataFrame(
-        rows, columns=["instance", "database", "username", "password"]
-    )
+    return pd.DataFrame(rows, columns=["instance", "database", "username", "password"])
 
 
 def _capture_dumps(*, db_type, rows, container, dump_tool="mariadb-dump"):