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/tsconfig.json

@@ -0,0 +1,25 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "compilerOptions": {
+    "target": "ES2022",
+    "lib": ["dom", "dom.iterable", "esnext"],
+    "allowJs": false,
+    "skipLibCheck": true,
+    "strict": true,
+    "noEmit": true,
+    "esModuleInterop": true,
+    "module": "esnext",
+    "moduleResolution": "bundler",
+    "resolveJsonModule": true,
+    "isolatedModules": true,
+    "jsx": "preserve",
+    "incremental": true,
+    "plugins": [{ "name": "next" }],
+    "baseUrl": ".",
+    "paths": {
+      "@/*": ["./src/*"]
+    }
+  },
+  "include": ["next-env.d.ts", "src/**/*.ts", "src/**/*.tsx", ".next/types/**/*.ts"],
+  "exclude": ["node_modules"]
+}