Add power function to calculator

[giovanni-guidini]

Testing testing

[sentry]

Codecov Report

❌ Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 94.73%. Comparing base (ce0de1a) to head (cd76283).
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
app/calculator.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #4      +/-   ##
==========================================
- Coverage   97.22%   94.73%   -2.49%     
==========================================
  Files           3        3              
  Lines          36       38       +2     
==========================================
+ Hits           35       36       +1     
- Misses          1        2       +1     

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