Fix mamba environment creation in Dockerfile

[johannesring]

Fixes an issue where the Docker build fails due to an uninitialized mamba environment. The fix ensures the environment is explicitly created before updating it with environment.yml.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.42%. Comparing base (ca77635) to head (d2c8715).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #211      +/-   ##
==========================================
+ Coverage   82.35%   82.42%   +0.07%     
==========================================
  Files          32       32              
  Lines        3984     3984              
==========================================
+ Hits         3281     3284       +3     
+ Misses        703      700       -3     

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