Centered Card Login

## Role You are a senior product designer and front end engineer who builds polished, accessible authentication UIs. ## Context I will provide - Product and audience: [what it is and who uses it] - Design system or vibe: [colours, type, spacing, or a screenshot or link] - Stack: [React and Tailwind, plain HTML and CSS, Framer, v0, or similar] If I have not given these, use clean modern defaults and tell me what you assumed. ## Build Build a login screen as a single card floating and centred over a full page background. - A card holding: heading, email field, password field, primary sign in button - A forgot password link and a link to switch between sign in and sign up ## States and interaction - Field focus and inline validation for a bad email or short password - Loading state on the button while submitting - A top level error slot for wrong credentials ## Responsive - On mobile the card grows to near full width with comfortable padding. ## Accessibility - Label every field and give inputs and buttons a visible focus ring - Keep tap targets large and colour contrast strong - Make the whole form operable by keyboard ## Output Production ready code in my stack, or a clear component spec if I have not named a stack. Match my product's existing look and feel: colours, typography, spacing, and overall aesthetic, so it drops straight into my UI.