[LoginPage] Add `<LoginPage>` component

[kiaking]

We use exact same login page for almost all apps. Would be nice to have this component built into Sefirot.

Should look something like this.

<SLoginPage
  cover="https://cover-image.jpg/"
  cover-title="Tokyo in the Night"
  cover-photographer="John Doe"
  :actions="[
    { type: "google", onClick: () => { /* Handle login */ } }
  ]"
/>