Implement design review changes

src/App.scss

src/App.tsx

src/components/Avatar.tsx

src/components/Button.scss

src/components/Button.stories.tsx

src/components/Button.tsx

src/components/ClientSelection.tsx

src/components/ClientTile.scss

src/components/CreateLinkTile.scss

src/components/CreateLinkTile.tsx

src/components/Footer.scss

src/components/Footer.tsx

src/components/HomeserverOptions.scss

src/components/HomeserverOptions.stories.tsx

src/components/HomeserverOptions.tsx

src/components/Input.scss

src/components/Input.tsx

src/components/InviteTile.scss

src/components/InviteTile.tsx

src/components/LinkPreview.tsx