fix(release): date changelog entries without a ruff-version-dependent noqa

ruff 0.16 flags date.today() (DTZ011) while 0.17 drops that rule from its defaults and flags the noqa as unused (RUF100), so CI's unpinned ruff failed lint-python. datetime.now().astimezone().date() yields the same local date and passes both, matching debian.py and rpm_changelog.py.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/pkgmgr/actions/release/files/changelog_md.py

@@ -3,7 +3,7 @@ from __future__ import annotations
 import os
 import re
 import sys
-from datetime import date
+from datetime import datetime
 
 from .changelog_lint import (
     ChangelogLintError,
@@ -69,7 +69,7 @@ def update_changelog(
     missing) and above any existing release entries, so the result stays
     markdown-lint-clean (MD041 first-line-h1, MD012 no-multiple-blanks).
     """
-    today = date.today().isoformat()  # noqa: DTZ011 - changelog dates are local calendar dates
+    today = datetime.now().astimezone().date().isoformat()
 
     def _entry_for(raw: str) -> tuple[str, str]:
         body = transform_changelog_message(raw).strip() or f"Release {new_version}"