build(lint): gate make test on a clean ruff run

ruff was never wired into this repository: no target, no CI step, no pin.
It reported 45 findings across sources and tests, so nothing enforced
what the codebase already mostly followed.

Adds `make ruff` (check + format --check), `make ruff-fix`, and `make
lint` as its alias, and makes `make test` run lint as a fourth parallel
spur. The CI workflow calls `make test`, so it is covered there too. The
linter is pinned in a `lint` extra: a ruff minor bump changes which rules
fire, and with the suite gating on a clean run an unpinned linter would
fail it on an unrelated day.

The 45 findings are fixed rather than configured away. Three needed a
decision instead of the mechanical fix:

- The generation timestamp keeps its local wall clock (DTZ005 waived).
  Generations sort by that name, and UTC would order new ones before the
  existing ones wherever the offset is positive - "newest generation" is
  what every restore path selects on.
- The per-volume `copy` closure now binds volume_name and vol_dir as
  default arguments (B023). It only worked because it is called inside
  the same iteration.
- The two CLI top-level handlers keep their blind except (BLE001
  waived): turning any failure into exit 1 is what a CLI boundary is
  for. The two in run.py did not need it and were narrowed to what they
  actually catch.

Also drops the comments that restate the code: the section banners in
restore/__main__.py, the filename repeated as line 1 of nine test files,
step narration above the statement it narrates, and a block in app.py
documenting parameters that had moved to another module. What names a
trip-wire stays - the snapshot destination rule, the mysql-binary
absence in MariaDB 11 images, the session-scoped FOREIGN_KEY_CHECKS, the
spooled temp file for multi-GB dumps, and the negative control that
loses its discriminating power if it ever passes.

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

tests/e2e/snapshot_db_driver.py

@@ -12,8 +12,8 @@ import sys
 
 sys.path.insert(0, "/src")
 
-from baudolo.backup.snapshot import SnapshotError, volume_snapshot  # noqa: E402
-from baudolo.backup.volume import backup_volume  # noqa: E402
+from baudolo.backup.snapshot import SnapshotError, volume_snapshot
+from baudolo.backup.volume import backup_volume
 
 SUBJECT = "/subject/docker"
 VOLUME = "mariadb_data"
@@ -23,7 +23,9 @@ GENERATION = f"{VERSIONS}/20260731"
 
 
 def shell(command: str) -> list[str]:
-    proc = subprocess.run(command, shell=True, capture_output=True, text=True)
+    proc = subprocess.run(
+        command, shell=True, capture_output=True, text=True, check=False
+    )
     if proc.returncode != 0:
         raise SnapshotError(
             f"{command} exited {proc.returncode}: {proc.stderr.strip()}"