[User Story] - As a logged-in user, I want to log out of the system securely to prevent unauthorized access to my account.

[ichirokentaro]

1. Given that I am a logged-in user,
   When I click on the 'Logout' button,
   Then I should be logged out of the system.

2. Given that I have logged out,
   When I attempt to access any page that requires authentication,
   Then I should be redirected to the login page.

3. Given that I have logged out,
   When I close the browser and reopen it,
   Then I should not be logged in to the system.

4. Given that I have logged out,
   When I try to use the old session cookie,
   Then the system should not recognize it as a valid session.

5. Given that I have logged out,
   When I view my browser's history,
   Then I should not be able to see sensitive information from my previous session.