security: pin axios to 1.13.4 — supply chain attack on 1.14.1

CVE: axios@1.14.1 pulls plain-crypto-js@4.2.1 (malware dropper)
Ref: https://x.com/feross

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: web3dev1337

diff-viewer/client/package.json

@@ -16,7 +16,7 @@
     "@anthropic-ai/sdk": "^0.56.0",
     "@monaco-editor/react": "^4.7.0",
     "@vitejs/plugin-react": "^5.1.3",
-    "axios": "^1.13.4",
+    "axios": "1.13.4",
     "dompurify": "^3.1.7",
     "marked": "^14.1.3",
     "mermaid": "^10.9.3",