Design a toast notification for a sign-in page that appears when a user either successfully logs in or encounters an error during the login process. The toast should be visually subtle yet clear enough to catch the user's attention. It should appear at the top or bottom of the page, sliding in smoothly and fading out after a few seconds unless dismissed by the user.
For a successful login, the toast should display a message in a positive tone with a green background, such as 'Welcome back! You've successfully logged in.' For an error, the message should be informative and direct, with a red background, such as 'Error: Incorrect username or password. Please try again.'
Include a small icon next to the text that corresponds with the message type—a checkmark for success and an exclamation mark for an error. The design of the toast should be clean and align with the website's overall aesthetic, using rounded corners and modern typography. Ensure that the toast is responsive | A shadcn/ui and v0 generation - v0
