feat(ui): update Card and Badge with Warm Precision styling

Card: rounded-lg → rounded-sm, border-border → border-border-default
Badge: rounded-md → rounded-sm, border-border → border-border-default

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/ui/badge.tsx

@@ -10,8 +10,8 @@ function Badge({ className, color, children, ...props }: BadgeProps) {
   return (
     <span
       className={cn(
-        'inline-flex items-center rounded-md px-1.5 py-0.5 text-xs font-medium border',
+        'inline-flex items-center rounded-sm px-1.5 py-0.5 text-xs font-medium border',
-        !color && 'border-border bg-elevated text-text-secondary',
+        !color && 'border-border-default bg-elevated text-text-secondary',
         className,
       )}
       style={style}

frontend/src/components/ui/card.tsx

@@ -6,7 +6,7 @@ const Card = React.forwardRef<HTMLDivElement, React.HTMLAttributes<HTMLDivElemen
     <div
       ref={ref}
       className={cn(
-        'rounded-lg border border-border bg-panel text-text-primary',
+        'rounded-sm border border-border-default bg-panel text-text-primary',
         className,
       )}
       {...props}