fix: Fix Sienna reserve requirement timeseries scaling

[akrivi]

This PR normalizes each ReEDS hourly reserve requirements profile (in MW) by its peak, which preserves the original MW requirements after PowerSystems serialization and ensures PowerSimulations receives the correct non-zero reserve requirements.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 91.17647% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.32%. Comparing base (2af872f) to head (2349a24).

Files with missing lines	Patch %	Lines
...-to-sienna/src/r2x_reeds_to_sienna/getter_utils.py	90.90%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #313      +/-   ##
==========================================
+ Coverage   85.30%   85.32%   +0.01%     
==========================================
  Files          20       20              
  Lines        5567     5593      +26     
==========================================
+ Hits         4749     4772      +23     
- Misses        818      821       +3     

Files with missing lines	Coverage Δ
...s-to-sienna/src/r2x_reeds_to_sienna/translation.py	100.00% <100.00%> (ø)
...-to-sienna/src/r2x_reeds_to_sienna/getter_utils.py	85.10% <90.90%> (+0.62%)	⬆️

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