fix: Fix week overflow navigation

[daelusion]

Pull Request Description

Fixes calculation of dates when navigating between weeks/months with overflow

Changes Proposed

• incrementMonth and decrementMonth functions handle updating the day of the provided date
• Add JSDocs for month/day calculators

Related Issues

Fixes #221

Checklist

• I have read the contribution guidelines and code of conduct.
• I have tested the changes locally and they are working as expected.
• I have added appropriate comments and documentation for the code changes.
• My code follows the coding style and standards of this project.
• I have rebased my branch on the latest main (or master) branch.
• All tests (if applicable) have passed successfully.
• I have run linters and fixed any issues.
• I have checked for any potential security issues or vulnerabilities.