fix: add timeout to PyPI update check to prevent hanging offline

[bigcat88]

requests.get() in check_for_newer_pypi_version() had no timeout, causing comfy launch, comfy env, and comfy install to hang indefinitely in offline or containerized environments.

Added a 3-second timeout and a logging.warning() on failure so it fails gracefully instead of blocking forever. Added tests covering newer version detection, same version, timeout, connection error, and HTTP error scenarios.

Closes #175. Supersedes #183 (that PR also fixed config_manager bool handling and tracking, both of which have been addressed separately since then).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@            Coverage Diff             @@
##             main     #378      +/-   ##
==========================================
+ Coverage   62.87%   62.99%   +0.11%     
==========================================
  Files          33       33              
  Lines        3688     3691       +3     
==========================================
+ Hits         2319     2325       +6     
+ Misses       1369     1366       -3     

Files with missing lines	Coverage Δ
comfy_cli/update.py	91.89% <100.00%> (+9.53%)	⬆️

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