[backend/frontend] update messages and translations for decay (#2859)

[SouadHadjiat]

Proposed changes

• Add missing translations for decay settings
• Update built-in decay rules names

Related issues

• Decay settings for Indicators scores #2859

Checklist

• I consider the submitted work as finished
• I tested the code for its functionality
• I wrote test cases for the relevant uses case
• I added/update the relevant documentation (either on github or on notion)
• Where necessary I refactored code to improve the overall quality

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (2e7eadf) 65.44% compared to head (8981a27) 66.03%.
Report is 7 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5948      +/-   ##
==========================================
+ Coverage   65.44%   66.03%   +0.58%     
==========================================
  Files         539      539              
  Lines       63059    63253     +194     
  Branches     5051     5503     +452     
==========================================
+ Hits        41271    41771     +500     
+ Misses      21788    21482     -306     

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