feat(psn): add PlayStation link card and PSN import

Settings card to link and unlink with the NPSSO, shows the expiry
date. Import page gets a PSN source; blocked when the link has ended.
English and German texts.

src/pages/SettingsPage.steam.test.jsx

@@ -33,6 +33,7 @@ function renderPage(me, {redirectUrl = STEAM_URL, entry = '/settings'} = {}) {
         'POST /api/auth/refresh': noBody,
         'GET /api/version': json(404, {}),
         'GET /api/follows': json(200, {following: [], followers: []}),
+        'GET /api/library/psn-account': json(200, {enabled: false, linked: false}),
     });
     renderWithProviders(<SettingsPage/>, {path: '/settings', entries: [entry]});
 }