Fix: Hide Sidebar and Chat UI on Login Screen

[PragnyaKhandelwal]

Issue Addressed:
When accessing the login page, the sidebar and chat interface were still visible in the background. This was confusing to users and exposed post-login UI before authentication.

What Was Happening:

• UI elements like sidebar, chatbot tone, and chatbox were always being rendered.
• There was no check to restrict visibility based on login state.

Suggested Fix (What I Can Implement):

• Introduce a login state flag using st.session_state['is_logged_in'] to track user authentication status.
• Wrap all post-login UI elements (such as the sidebar, chatbot tone selector, and chat interface) within an if st.session_state['is_logged_in']: condition.
• Ensure that only the login form is visible until the user successfully logs in.
• Trigger a st.rerun() after successful login to refresh the app UI and render the appropriate components.

I would like to contribute here and work on this in resolving the issue.

[eccentriccoder01]

@PragnyaKhandelwal there's a bit of confusion and conflict relating authentication. Please check #68 (comment) for a detailing and share your insights. Thanks!