fix: set ruff target-version to py39 and upgrade django (#555)

Set ruff target-version to py39 (minimum supported Python) instead of
py314 to prevent PEP 758 formatting (parentheses-free except clauses)
that would break compatibility with Python < 3.14.

Bump django minimum from >=5.0.8 to >=5.2.11 to resolve Dependabot
security alerts (SQL injection, DoS, directory traversal).

Author: fgmacedo

AGENTS.md

@@ -72,7 +72,7 @@ uv run mypy statemachine/ tests/
 
 ## Code style
 
-- **Formatter/Linter:** ruff (line length 99, target Python 3.14)
+- **Formatter/Linter:** ruff (line length 99, target Python 3.9)
 - **Rules:** pycodestyle, pyflakes, isort, pyupgrade, flake8-comprehensions, flake8-bugbear, flake8-pytest-style
 - **Imports:** single-line, sorted by isort
 - **Docstrings:** Google convention

pyproject.toml

@@ -45,7 +45,7 @@ dev = [
     "pytest-benchmark >=4.0.0",
     "pytest-asyncio",
     "pydot",
-    "django >=5.0.8; python_version >='3.10'",
+    "django >=5.2.11; python_version >='3.10'",
     "pytest-django >=4.8.0; python_version >'3.8'",
     "Sphinx; python_version >'3.8'",
     "sphinx-gallery; python_version >'3.8'",
@@ -129,7 +129,7 @@ ignore_missing_imports = true
 src = ["statemachine"]
 
 line-length = 99
-target-version = "py314"
+target-version = "py39"
 
 # Exclude a variety of commonly ignored directories.
 exclude = [