fix: backend/package.json & backend/package-lock.json to reduce vulnerabilities

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-JSONWEBTOKEN-3180026
- https://snyk.io/vuln/SNYK-JS-JSONWEBTOKEN-3180024
- https://snyk.io/vuln/SNYK-JS-JSONWEBTOKEN-3180022
- https://snyk.io/vuln/SNYK-JS-EXPRESS-6474509

Author: snyk-bot

backend/package-lock.json

@@ -12,8 +12,8 @@
   "dependencies": {
     "bcryptjs": "^2.4.3",
     "body-parser": "^1.20.0",
-    "express": "^4.18.1",
-    "jsonwebtoken": "^8.5.1",
+    "express": "^4.19.2",
+    "jsonwebtoken": "^9.0.0",
     "uuid": "^9.0.0"
   }
 }