ui: update react-router-dom to 7.12.0 (#456)

Update react-router-dom from 7.6.2 to 7.12.0 to address security vulnerability.

- Updated dependency in package.json
- Regenerated package-lock.json
- Verified build passes successfully
- Confirmed 0 vulnerabilities with npm audit

Co-authored-by: Claude <noreply@anthropic.com>

ui/package.json

@@ -14,7 +14,7 @@
     "react-dom": "^19.1.0",
     "react-icons": "^5.5.0",
     "react-resizable-panels": "^3.0.4",
-    "react-router-dom": "^7.6.2"
+    "react-router-dom": "^7.12.0"
   },
   "devDependencies": {
     "@eslint/js": "^9.25.0",