fix(ui): GIF picker surface tokens + background swatch chrome (N8, N70)

- N8: GifPicker non-TDS container used undefined var(--bg-surface) + raw
  rgba/12px/boxShadow. Switch to folds tokens (color.Surface.Container,
  config.radii.R400, color.Surface.ContainerLine, color.Other.Shadow).
  TDS branch keeps its --lt-* glow chrome.
- N70: ChatBgGrid/SeasonalBgGrid swatch buttons moved chrome (radius, border,
  hover, keyboard :focus-visible ring, selected via data-selected) into shared
  BgSwatch.css.ts using design tokens; only per-swatch size + live preview
  background stay inline (custom preview tiles, not MenuItem/Chip candidates).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/components/GifPicker.tsx

@@ -2,7 +2,7 @@ import React, { useCallback } from 'react';
 import FocusTrap from 'focus-trap-react';
 import { Grid, SearchBar, SearchContext, SearchContextManager } from '@giphy/react-components';
 import { IGif } from '@giphy/js-types';
-import { Box } from 'folds';
+import { Box, color, config } from 'folds';
 import { useSetting } from '../state/hooks/settings';
 import { settingsAtom } from '../state/settings';
 
@@ -91,11 +91,11 @@ export function GifPicker({ apiKey, onSelect, requestClose }: GifPickerProps) {
         width: `${PICKER_WIDTH}px`,
       }
     : {
-        background: 'var(--bg-surface)',
-        border: '1px solid rgba(255,255,255,0.08)',
-        borderRadius: '12px',
+        background: color.Surface.Container,
+        border: `${config.borderWidth.B300} solid ${color.Surface.ContainerLine}`,
+        borderRadius: config.radii.R400,
         overflow: 'hidden',
-        boxShadow: '0 8px 32px rgba(0,0,0,0.4)',
+        boxShadow: color.Other.Shadow,
         width: `${PICKER_WIDTH}px`,
       };