Issue regarding signin and signup

[dipesh-2874]

1. After signing up the page is redirected to the signin page. Instead of that it might be directed to the homepage.
2. The adding new user logic overwrites the previous user so we can't check if the user already exists or not so I wanna implement a slightly different logic so that we can check whether there is already an user with same username and counter the overwriting issue.

for this I'll use HTML, JS and Localstorage

please assign me this under JWOC-2026