refactor(admin): CRM을 apps/admin 독립 프로젝트로 분리

- apps/web에서 admin 라우트/가드/sidebar 링크 제거
- apps/admin: 독립 Next.js 앱 (포트 3001)
  - 자체 login/unauthorized/auth callback
  - admin-sidebar: Overview/Users/Subscriptions/Usage
  - requireAdmin() 가드: profile.role='admin' 체크
- monorepo workspace에 apps/admin 등록

apps/admin/package.json

@@ -0,0 +1,33 @@
+{
+  "name": "@d3ro/admin",
+  "version": "1.0.0",
+  "private": true,
+  "description": "D3RO Voice Admin CRM — SaaS 관리 도구",
+  "scripts": {
+    "dev": "next dev --port 3001",
+    "build": "next build",
+    "start": "next start --port 3001",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@d3ro/api-client": "*",
+    "@d3ro/core": "*",
+    "@d3ro/ui": "*",
+    "@emotion/cache": "^11.14.0",
+    "@emotion/react": "^11.14.0",
+    "@emotion/styled": "^11.14.0",
+    "@mui/icons-material": "^7.0.0",
+    "@mui/material": "^7.0.0",
+    "@mui/material-nextjs": "^7.0.0",
+    "@supabase/ssr": "^0.10.0",
+    "@supabase/supabase-js": "^2.103.0",
+    "next": "^15.0.0",
+    "react": "^19.0.0",
+    "react-dom": "^19.0.0"
+  },
+  "devDependencies": {
+    "@types/node": "^22.13.0",
+    "@types/react": "^19.0.0",
+    "@types/react-dom": "^19.0.0"
+  }
+}