Bump pytz from 2025.2 to 2026.4

Bumps [pytz](https://github.com/stub42/pytz) from 2025.2 to 2026.4.
- [Release notes](https://github.com/stub42/pytz/releases)
- [Commits](https://github.com/stub42/pytz/compare/release_2025.2...release_2026.4)

---
updated-dependencies:
- dependency-name: pytz
  dependency-version: '2026.4'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

pyproject.toml

@@ -20,7 +20,7 @@ dependencies = [
     "premailer~=3.10",
     "psycopg2-binary~=2.9",
     "pypdf~=6.19",
-    "pytz~=2025.2",
+    "pytz>=2025.2,<2027.0",
     "reportlab~=4.4",
     "simplejson~=3.20",
     "whitenoise~=6.12",