style(frontend): taste-skill 반영 — 오프블랙 글씨, 버튼 알약/카드 10px 분리, 눌림 피드백

- .agents/skills: Leonxlnx/taste-skill 3개 설치(랜딩용이라 채팅 앱엔 일부만 적용)
- samsung 팔레트: foreground #000→#111. 전역 --radius 20 을 10 으로 내리고 --radius-pill 로 버튼만 알약
- Button: rounded-[var(--radius-pill,var(--radius-md))], active:scale-[0.98]

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

2_frontend/src/shared/ui/button.tsx

@@ -5,7 +5,9 @@ import { cva, type VariantProps } from "class-variance-authority"
 import { cn } from "@/lib/utils/cn"
 
 const buttonVariants = cva(
-  "inline-flex items-center justify-center gap-2 whitespace-nowrap rounded-md text-sm font-medium ring-offset-background transition-colors focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:size-4 [&_svg]:shrink-0",
+  // rounded-[var(--radius-pill,var(--radius-md))]: 팔레트가 --radius-pill 을 주면 알약, 아니면 기존 md.
+  // active:scale-[0.98]: 눌림 피드백(정적 hover 만 있으면 밋밋함).
+  "inline-flex items-center justify-center gap-2 whitespace-nowrap rounded-[var(--radius-pill,var(--radius-md))] text-sm font-medium ring-offset-background transition-[color,background-color,transform] active:scale-[0.98] focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50 [&_svg]:pointer-events-none [&_svg]:size-4 [&_svg]:shrink-0",
   {
     variants: {
       variant: {
@@ -18,8 +20,8 @@ const buttonVariants = cva(
       },
       size: {
         default: "h-10 px-4 py-2",
-        sm: "h-9 rounded-md px-3",
-        lg: "h-11 rounded-md px-8",
+        sm: "h-9 px-3",
+        lg: "h-11 px-8",
         icon: "h-10 w-10",
       },
     },