ref(frontend|backend|potal): Only build Docker images

[cleptric]

We do not need these images to be pushed but should still run the action to see if our containers build.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (main@7f7e967). Click here to learn what that means.
Patch has no changes to coverable lines.

❗ Current head a471b89 differs from pull request most recent head 8bdf297. Consider uploading reports for the commit 8bdf297 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #72   +/-   ##
=======================================
  Coverage        ?   35.50%           
  Complexity      ?      242           
=======================================
  Files           ?       48           
  Lines           ?     1963           
  Branches        ?        0           
=======================================
  Hits            ?      697           
  Misses          ?     1266           
  Partials        ?        0           

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