Implement login functionality

[Japoivvb]

Describe the solution you'd like
Currently, the app does not have a login mechanism. To improve security and user experience, we should:
Add a new login pane before the main people menu (after data storage menu) that prompts the user for their username and password.
Validate the entered credentials to ensure the user can only access the app if the login is successful.

Additional context

• Login Pane:

Create a new login pane that will appear before the main menu.
Include fields for the user to enter a username and password.
Add a "Login" button that the user can click after entering their credentials.

• User and Password Fields:

The login pane should have an username field and a password field (password should be masked to hide characters as they are typed).

• Login Validation:

Implement backend logic to verify the entered credentials against a stored list (or database) of valid users and passwords.
If the login is successful, the user will be redirected to the main menu or app.
If the login fails, display an error message like "Invalid username or password."

• Menu or App Changes:

Ensure that the main menu and app features are only accessible after the user successfully logs in.

• Error Handling:

If the user enters invalid credentials, prevent access to the main menu and show an error message: "Invalid username or password."

Expected sample