Fix mypy Python version to match system Python 3.12

- Corrected mypy python_version from 3.9 to 3.12 to match system Python
- Type checking still passes with all annotations intact

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

pyproject.toml

@@ -94,7 +94,7 @@ known_first_party = ["wikijs"]
 known_third_party = ["pytest", "requests", "pydantic"]
 
 [tool.mypy]
-python_version = "3.9"
+python_version = "3.12"
 warn_return_any = true
 warn_unused_configs = true
 disallow_untyped_defs = true