Run main process in docker image via tini

[acelaya]

Add tini to prod docker image, and run server through it.

As opposed to node, tini properly handles signals.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 73.40%. Comparing base (85d01e2) to head (ea5f3d7).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #580   +/-   ##
=======================================
  Coverage   73.40%   73.40%           
=======================================
  Files          75       75           
  Lines        2410     2410           
  Branches      387      387           
=======================================
  Hits         1769     1769           
  Misses        255      255           
  Partials      386      386           

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