chore(theme): the login's fixed light colours move with its code step into MfaCodeStep

The login card is a fixed light surface whose text colours are written out,
not tokens. Four of them moved with the two-factor step, so the baseline moves
them too: 58 to 54 for the page, 4 for the new component, the same total.

client/scripts/theme-baseline.json

@@ -294,7 +294,7 @@
   "pages/JourneyDetailPage.tsx": 53,
   "pages/JourneyPage.tsx": 64,
   "pages/JourneyPublicPage.tsx": 113,
-  "pages/LoginPage.tsx": 58,
+  "pages/LoginPage.tsx": 54,
   "pages/OAuthAuthorizePage.tsx": 33,
   "pages/PluginPage.tsx": 1,
   "pages/ResetPasswordPage.tsx": 23,
@@ -302,6 +302,7 @@
   "pages/VacayPage.tsx": 13,
   "pages/atlas/useAtlas.ts": 2,
   "pages/collections/useCollections.ts": 1,
+  "pages/login/MfaCodeStep.tsx": 4,
   "pages/sharedTrip/SharedChrome.tsx": 2,
   "pages/sharedTrip/SharedMap.tsx": 1,
   "pages/tripPlanner/ListsContainer.tsx": 1,