Fix issues in parsing configuration files due to Pydantic upgrade

[nnansters]

New treatment of Optional in Pydantic 2 was causing issues with the CLI.

This PR aims to fix that behavior.

[codecov]

Codecov Report

Attention: Patch coverage is 95.65217% with 1 line in your changes missing coverage. Please review.

Project coverage is 74.72%. Comparing base (522a3bc) to head (cbde8b1).
Report is 20 commits behind head on main.

Files with missing lines	Patch %	Lines
nannyml/config.py	95.65%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #421   +/-   ##
=======================================
  Coverage   74.72%   74.72%           
=======================================
  Files         109      109           
  Lines        9702     9702           
  Branches     1750     1750           
=======================================
  Hits         7250     7250           
  Misses       1965     1965           
  Partials      487      487           

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