feat(scripts): Add a check-github-sync script

[effigies]

Also adds a health-check CI job to run this once a week.

Working: https://github.com/OpenNeuroOrg/openneuro/actions/runs/14364296414/job/40273360149

xref #3407

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.93%. Comparing base (5f21c97) to head (98f2870).
Report is 8 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3410   +/-   ##
=======================================
  Coverage   45.93%   45.93%           
=======================================
  Files         577      577           
  Lines       39524    39524           
  Branches     1286     1286           
=======================================
  Hits        18156    18156           
  Misses      21183    21183           
  Partials      185      185           

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[effigies]

@nellh I think this can be merged if you're happy with it. It will only run on a schedule, manual triggers, or pushing to this branch. We can remove this branch from the triggers, but it could be useful to keep it around for testing patches.

[effigies]

With #3407 complete, and redis caches dropped, this check is now passing.