Support Python 3.13 (relax python_requires upper bound)

[LMartinezEXEX]

Installing llm-guard on Python 3.13.2 is blocked by the project’s python_requires constraint, which currently excludes 3.13 (>=3.9, <3.13). Please relax the upper bound (or remove it) to allow Python 3.13. 

Steps to Reproduce

python --version
# Python 3.13.2
pip install llm-guard
# Resolver rejects because requires-python is <3.13

Expected Behavior

pip install llm-guard succeeds on Python 3.13.

Actual Behavior

Installation is skipped/blocked due to the requires-python upper bound.

Environment

• Python: 3.13.2
• Package manager: pip
• OS: (macOS/Linux/Windows) — n/a to the metadata error

Rationale

• Python 3.13 has been stable since Oct 7, 2024 and is widely adopted.
• The project previously relaxed constraints to add 3.12 support; this request follows the same trajectory for 3.13. 

Proposed Change

• In pyproject.toml, update:
  • Option A (preferred): requires-python = ">=3.9" (drop the upper bound)
  • Option B: requires-python = ">=3.9, <3.14" (temporarily allow 3.13)
• Add/confirm CI runs on Python 3.13 (unit tests, typing, and key integrations).

Additional Context

If there are known 3.13 incompatibilities in dependencies, a tracking checklist in this issue would help downstream users plan upgrades.

[hemkumarm]

Can anyone please look into this issue, @asofter.