Implement design system: blob background, glassmorphism, softer corners

- globals.css: add blob keyframe animation (9s ease-in-out infinite)
- layout.tsx: add fixed background layer with 24px grid pattern and two
  animated blurred blobs (primary/5 color) that drift behind all content
- Navigation.tsx: bg-background/80 + backdrop-blur-md + border-border/50
- Sidebar.tsx: same glassmorphism treatment
- card.tsx: rounded-2xl (up from rounded-lg), bg-card/80 + backdrop-blur-sm
  so the blob color bleeds subtly through card surfaces

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

src/components/ui/card.tsx

@@ -12,7 +12,7 @@ function Card({
       data-slot="card"
       data-size={size}
       className={cn(
-        "group/card flex flex-col gap-4 overflow-hidden rounded-lg bg-card py-4 text-sm text-card-foreground ring-1 ring-foreground/10 has-[>img:first-child]:pt-0 data-[size=sm]:gap-3 data-[size=sm]:py-3 *:[img:first-child]:rounded-t-lg *:[img:last-child]:rounded-b-lg",
+        "group/card flex flex-col gap-4 overflow-hidden rounded-2xl bg-card/80 py-4 text-sm text-card-foreground ring-1 ring-foreground/10 backdrop-blur-sm has-[>img:first-child]:pt-0 data-[size=sm]:gap-3 data-[size=sm]:py-3 *:[img:first-child]:rounded-t-2xl *:[img:last-child]:rounded-b-2xl",
         className
       )}
       {...props}
@@ -25,7 +25,7 @@ function CardHeader({ className, ...props }: React.ComponentProps<"div">) {
     <div
       data-slot="card-header"
       className={cn(
-        "group/card-header @container/card-header grid auto-rows-min items-start gap-1 rounded-t-lg px-4 group-data-[size=sm]/card:px-3 has-data-[slot=card-action]:grid-cols-[1fr_auto] has-data-[slot=card-description]:grid-rows-[auto_auto] [.border-b]:pb-4 group-data-[size=sm]/card:[.border-b]:pb-3",
+        "group/card-header @container/card-header grid auto-rows-min items-start gap-1 rounded-t-2xl px-4 group-data-[size=sm]/card:px-3 has-data-[slot=card-action]:grid-cols-[1fr_auto] has-data-[slot=card-description]:grid-rows-[auto_auto] [.border-b]:pb-4 group-data-[size=sm]/card:[.border-b]:pb-3",
         className
       )}
       {...props}