fix: index.html 헤더 링크 추가 및 tester.html CSV 한글 깨짐 방지(BOM 추가)

dap-gateway/src/main/resources/static/tester.html

@@ -331,7 +331,7 @@
                 csvContent += `${category},${name},${status},${latency},${payloadStr},${responseStr}\n`;
             });
             
-            const blob = new Blob([csvContent], { type: 'text/csv;charset=utf-8;' });
+            const blob = new Blob(['\uFEFF' + csvContent], { type: 'text/csv;charset=utf-8;' });
             const url = URL.createObjectURL(blob);
             const link = document.createElement("a");
             link.setAttribute("href", url);