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_app_databases_csv.py

@@ -1,8 +1,8 @@
 import io
-import os
 import tempfile
 import unittest
 from contextlib import redirect_stderr
+from pathlib import Path
 
 import pandas as pd
 
@@ -15,7 +15,7 @@ EXPECTED_COLUMNS = ["instance", "database", "username", "password"]
 class TestLoadDatabasesDf(unittest.TestCase):
     def test_missing_csv_is_handled_with_warning_and_empty_df(self) -> None:
         with tempfile.TemporaryDirectory() as td:
-            missing_path = os.path.join(td, "does-not-exist.csv")
+            missing_path = str(Path(td) / "does-not-exist.csv")
 
             buf = io.StringIO()
             with redirect_stderr(buf):
@@ -31,8 +31,8 @@ class TestLoadDatabasesDf(unittest.TestCase):
 
     def test_empty_csv_is_handled_with_warning_and_empty_df(self) -> None:
         with tempfile.TemporaryDirectory() as td:
-            empty_path = os.path.join(td, "databases.csv")
-            with open(empty_path, "w", encoding="utf-8") as f:
+            empty_path = Path(td) / "databases.csv"
+            with empty_path.open("w", encoding="utf-8") as f:
                 f.write("")
 
             buf = io.StringIO()
@@ -49,10 +49,10 @@ class TestLoadDatabasesDf(unittest.TestCase):
 
     def test_valid_csv_loads_without_warning(self) -> None:
         with tempfile.TemporaryDirectory() as td:
-            csv_path = os.path.join(td, "databases.csv")
+            csv_path = Path(td) / "databases.csv"
 
             content = "instance;database;username;password\nmyapp;*;dbuser;secret\n"
-            with open(csv_path, "w", encoding="utf-8") as f:
+            with csv_path.open("w", encoding="utf-8") as f:
                 f.write(content)
 
             buf = io.StringIO()