feat: add OPTIONS HTTP method support and apply minor code cleanup

[DamianCzajkowski]

Summary

• Add OPTIONS to the list of allowed HTTP methods on the catch-all /{path:path} route, enabling CORS preflight and other OPTIONS-based requests.
• Modernize type annotations in __main__.py by replacing Optional[X] with X | None (PEP 604) and removing the unused import.
• Simplify an unnecessary f-string concatenation in utils.py.
• Update corresponding test assertions to include OPTIONS in the expected methods list.