fix(ui): make modal panel fully opaque and drop its backdrop blur

The panel sat at bg-cork-surface/95, so its backdrop-blur-xl only acted
on a 5% see-through sliver — cost without visible effect. Make the panel
fully opaque and remove the now-pointless blur layer.

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

Author: koki-develop

src/components/organisms/shell/Modal.tsx

@@ -123,7 +123,7 @@ function ModalContainer({
       />
       <m.div
         className={clsx(
-          "border-cork-border/60 bg-cork-surface/95 relative mx-4 max-h-[85vh] w-full overflow-y-auto rounded-2xl border p-6 shadow-2xl backdrop-blur-xl",
+          "border-cork-border/60 bg-cork-surface relative mx-4 max-h-[85vh] w-full overflow-y-auto rounded-2xl border p-6 shadow-2xl",
           maxWidthClassName,
           containerClassName,
         )}