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>

src/baudolo/backup/db.py

@@ -1,10 +1,9 @@
 from __future__ import annotations
 
+import logging
 import os
 import pathlib
 import re
-import logging
-from typing import Optional
 
 import pandas
 
@@ -22,7 +21,7 @@ def get_instance(container: str, database_containers: list[str]) -> str:
     return re.split(r"(_|-)(database|db|postgres)", container)[0]
 
 
-def _validate_database_value(value: Optional[str], *, instance: str) -> str:
+def _validate_database_value(value: str | None, *, instance: str) -> str:
     """
     Enforce explicit database semantics:
 
@@ -70,7 +69,7 @@ def backup_database(
     container: str,
     volume_dir: str,
     db_type: str,
-    databases_df: "pandas.DataFrame",
+    databases_df: pandas.DataFrame,
     database_containers: list[str],
 ) -> bool:
     """
@@ -97,7 +96,6 @@ def backup_database(
 
         db_value = _validate_database_value(raw_db, instance=instance_name)
 
-        # Explicit: dump ALL databases
         if db_value == "*":
             if db_type != "postgres":
                 raise ValueError(
@@ -110,7 +108,6 @@ def backup_database(
             produced = True
             continue
 
-        # Concrete database dump
         db_name = db_value
         dump_file = os.path.join(out_dir, f"{db_name}.backup.sql")
 
@@ -135,7 +132,6 @@ def backup_database(
                 _atomic_write_cmd(cmd, dump_file)
                 produced = True
             except BackupException as e:
-                # Explicit DB dump failed -> hard error
                 raise BackupException(
                     f"Postgres dump failed for instance '{instance_name}', "
                     f"database '{db_name}'. This database was explicitly configured "