Restyle prebuilt auth components with Tailwind (shadcn-ui inspired) and add animations

[3lvin-Kc]

Motivation

• Provide a small, opinionated, and attractive set of optional UI helpers so consumers can get a polished login/logout experience out-of-the-box.
• Use Tailwind (shadcn-ui inspired) styling and subtle animations to make the prebuilt components visually appealing while keeping them thin wrappers around the existing auth hooks.

Description

• Restyled LoginForm with Tailwind utility classes, improved focus/fallback states, a compact layout, and an animated spinner and transitions for submit/loading/error states.
• Restyled LogoutButton with matching Tailwind classes and a small loading spinner animation for consistent feedback.
• Centered the default AuthGate login view and made it use the new LoginForm as a visually pleasing fallback while preserving loginFallback, loadingFallback, and errorFallback props.
• Exported AuthGate, LoginForm, and LogoutButton from the public API and documented the Tailwind/shadcn-style expectation in README.md.

Testing

• No automated tests were run for these UI-only changes.
• Visual validation is expected to be done by consumers with Tailwind configured since the components rely on Tailwind utilities for the intended appearance and animations.

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Codex Task