fix: upgrade winston from 3.14.2 to 3.15.0

Snyk has created this PR to upgrade winston from 3.14.2 to 3.15.0.

See this package in npm:
winston

See this project in Snyk:
https://app.snyk.io/org/baderdean/project/0f8e176b-5f8b-457c-96ec-ede2a65658a3?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot

backend/package-lock.json

@@ -58,7 +58,7 @@
     "simple-oauth2": "^5.1.0",
     "stripe": "^13.11.0",
     "throttled-queue": "^2.1.4",
-    "winston": "^3.14.2",
+    "winston": "^3.15.0",
     "winston-loki": "^6.1.2",
     "xoauth2": "^1.2.0",
     "zod": "^3.23.8",