feat: Improve organization of HTML templates

[Mopsgamer]

Summary

Improve the separation and modularization of the ./client/templates/**/*.html files for better maintainability and scalability.

Feature Details

Currently, the ./client/templates/**/*.html files lack clear separation, leading to a
monolithic structure that is difficult to maintain. Refactoring the templates into
smaller, reusable components would enhance code readability, reusability, and
scalability.

Suggested improvements:

• Group related templates into dedicated directories.
• Implement a naming convention to distinguish different types of templates (e.g.,
  layout, partials, components).
• Ensure templates follow a DRY (Don't Repeat Yourself) principle.

Additional Information

Refactoring should be done incrementally to prevent breaking existing functionality.
Consider using template inheritance or includes where applicable.