Update the uv-metrics tutorial documentation

[ajslone]

This PR updates the uv-metrics + mlflow tutorial documentation, and adds a simple sanity-test script to test database connectivity.

[codecov]

Codecov Report

Merging #74 into master will increase coverage by 0.28%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master      #74      +/-   ##
==========================================
+ Coverage   51.52%   51.81%   +0.28%     
==========================================
  Files          31       31              
  Lines        3148     3148              
==========================================
+ Hits         1622     1631       +9     
+ Misses       1526     1517       -9     

Impacted Files	Coverage Δ
caliban/platform/gke/util.py	72.51% <0.00%> (+2.67%)	⬆️
caliban/util/auth.py	76.19% <0.00%> (+9.52%)	⬆️

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