Feature/upgrade deps and modernize tests

[SeanAdams10]

Description

Hi there - the current code base has all dependencies are pinned to 2022-era versions, would the maintainers welcome a PR to modernize? Note: the readme.md mentions that this is a fork with full credit to the original - this comment may need to be removed if you accept this to the main trunk.

Key changes

• Update Python requirement from 3.10 to >=3.13
• Upgrade all packages to latest stable versions across pyproject.toml,
  setup.py, server/requirements.txt, and Dockerfile (python:3.13-bookworm)
• Remove numpy<2 constraint, now using numpy 2.4.4
• Update tensorflow 2.19→2.21, ray 2.2→2.54.1, setuptools 77→82, and
  all other pinned dependencies
• Replace legacy import gym with import gymnasium in rllib.py and
  remove deprecated gym package from dependencies
• Fix Gymnasium env warnings: change observation_space from Box to
  Tuple(Box, Box), return obs tuples from reset()/step() instead of
  dicts, move metadata to info dict
• Add 14 new pytest tests (test_gym_env_warnings.py) verifying no
  gymnasium warnings and correct observation format
• Convert all 9 test files from unittest to pytest (testing/ and
  src/human_aware_rl/), removing all unittest.TestCase inheritance,
  setUp/tearDown → fixtures, self.assert* → plain assert
• Fix flaky test_mdp_serialization by using tempfile instead of shared
  path, and fix test_render_state_from_dict misnamed helper function
• Regenerate uv.lock with all updated dependencies

Potentially breaking changes (depends on usage)

• Python 3.10/3.11/3.12 no longer supported (now requires >=3.13)
• numpy 2.x: code using numpy 1.x-only APIs (e.g. removed type aliases like np.bool, np.int, np.float, np.object, np.str) will break.
  Pickled data using old numpy dtypes may trigger deprecation warnings.
• Gymnasium env API change: Overcooked.reset() and step() now return observation as a tuple of two numpy arrays instead of a dict with "both_agent_obs"/"overcooked_state"/"other_agent_env_idx" keys. "overcooked_state" and "other_agent_env_idx" are now in the info dict. observation_space is now Tuple(Box, Box) instead of Box.
• gym package removed: code importing gym must switch to gymnasium
• Flask upgraded 2.x→3.x and Flask-SocketIO 4.x→5.x in server requirements (different async handling, python-socketio 4.x→5.x)
• protobuf upgraded 3.x→7.x in server requirements (breaking API changes across major versions)
• Dockerfile base image changed from python:3.7-buster to python:3.13-bookworm

Checklist:

• All test cases are still passing
• No new functionality