chore(phase0): PortOne 잔재 제거 — 계좌이체 단일 소스 확정, saju 결제 CTA 제거

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

package.json

@@ -13,7 +13,6 @@
     "@anthropic-ai/sdk": "^0.79.0",
     "@google-analytics/data": "^5.2.1",
     "@google/generative-ai": "^0.24.1",
-    "@portone/browser-sdk": "^0.1.3",
     "@supabase/ssr": "^0.5.2",
     "@supabase/supabase-js": "^2.99.0",
     "clsx": "^2.1.1",