fix(mobile): language banner vs Ask-MSOS pill + guide button overflow

- On phones the language-suggestion banner sat at the bottom and the floating
  "Ask MSOS" pill (higher z-index) overlapped its bottom-right, hiding the
  dismiss (x) button. Raise the banner above the pill (bottom: 84px) so they
  stack and the x is fully visible and tappable.
- The success-screen "Read the welcome guide" button used the base .btn
  white-space:nowrap, so the long MK label overflowed the box on narrow
  screens. Allow .ms-success-links .btn to wrap (white-space: normal).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

css/components/_lang-banner.css

@@ -56,7 +56,9 @@
     .lang-suggest {
         left: 16px;
         right: 16px;
-        bottom: 16px;
+        /* sit above the floating "Ask MSOS" pill (bottom-right, z-index above
+           this banner) so it never covers the dismiss (×) button */
+        bottom: 84px;
         transform: translateY(24px);
         flex-wrap: wrap;
     }