Fix nginx validation in deploy pipeline

deploy_gb.sh

@@ -175,12 +175,16 @@ echo "  ✓ No critical errors in logs"
 
 # 6.2 Nginx 설정 검증
 echo "  Checking Nginx configuration..."
-if ! sudo nginx -t 2>&1 | grep -q "successful"; then
+NGINX_TEST_LOG=$(mktemp)
+if ! sudo nginx -t >"$NGINX_TEST_LOG" 2>&1; then
   echo "❌ Nginx configuration is invalid"
+  tail -50 "$NGINX_TEST_LOG" 2>/dev/null || true
+  rm -f "$NGINX_TEST_LOG"
   echo "🔙 Rolling back..."
   kill -9 $NEW_PID || true
   exit 1
 fi
+rm -f "$NGINX_TEST_LOG"
 echo "  ✓ Nginx configuration is valid"
 
 # 6.3 프로세스가 여전히 실행 중인지 확인