docs: add clear and more descriptive comments

[jaybxyz]

Summary

Add clear and descriptive comments on all the functions and logics.

Problem Definition

Some of the methods are missing comments and some logics need an explanation about why they should be that way.

Proposal

Scan through all the files in budget module and add or update comments to have clear and descriptive comments.

Tasks

• scan through client folder to improve comments
• scan through keeper folder to improve comments
• scan through simulation folder to improve comments
• scan through types folder to improve comments

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