docs: align admin password guidance

DOCKER_RUN.md

@@ -33,7 +33,7 @@ docker-compose ps
 - **URL**: http://localhost:5001/taxbaik/admin/login
 - **초기 계정**:
   - username: `admin`
-  - password: `admin123`
+  - password: `<TAXBAIK_ADMIN_TEST_PASSWORD>`
 - **기능**:
   - 대시보드 확인
   - 블로그 관리
@@ -105,7 +105,7 @@ curl -I http://localhost:5001/taxbaik/admin/login
 # 로그인 (쿠키 저장)
 curl -c cookies.txt -X POST http://localhost:5001/taxbaik/admin/login \
   -H "Content-Type: application/x-www-form-urlencoded" \
-  -d "username=admin&password=admin123"
+  -d "username=admin&password=<TAXBAIK_ADMIN_TEST_PASSWORD>"
 
 # 대시보드 접근 (쿠키 사용)
 curl -b cookies.txt http://localhost:5001/taxbaik/admin/dashboard