feat: premium redesign — DM Serif, refined palette, flat score badges

- Design tokens (ds.ts, theme.ts, scoreTheme.ts): new warm palette
  (#152642 navy, #f9f8f6 warm white, #e8e7e4 borders, #b8975a gold accent),
  flat score tier badges replacing CSS gradients, Inter + DM Serif Display typography
- Card components: white-background cards, DM Serif score numbers, max-2 badge
  chips with +N overflow tooltip, editorial score badge positioning
- Layout shell: gold left-accent nav active state, 64px top bar, outlined
  workspace chip, DM Serif page titles
- Shared atoms: GenericBadge (outlined/solid variants), ResultFilterBar
  (simplified chip styles), DecisionContextPanel (dot metrics, no left accent)
- Global replacement (118 files): #1e3a5f→#152642, #e2e8f0→#e8e7e4,
  #f4f6f9→#f9f8f6 — all handled via Node.js for proper UTF-8 safety

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/layout/UserMenu.tsx

@@ -45,7 +45,7 @@ export function UserMenu() {
   return (
     <>
       <IconButton onClick={handleOpen} size="small" sx={{ p: 0 }}>
-        <Avatar sx={{ width: 32, height: 32, fontSize: '0.75rem', bgcolor: '#1e3a5f' }}>
+        <Avatar sx={{ width: 32, height: 32, fontSize: '0.75rem', bgcolor: '#152642' }}>
           {initials}
         </Avatar>
       </IconButton>