fix: upgrade mini-css-extract-plugin from 2.7.2 to 2.7.6

Snyk has created this PR to upgrade mini-css-extract-plugin from 2.7.2 to 2.7.6.

See this package in npm:
https://www.npmjs.com/package/mini-css-extract-plugin

See this project in Snyk:
https://app.snyk.io/org/woodpile37/project/044862aa-1005-4f2f-af06-341513c0e0a2?utm_source=github&utm_medium=referral&page=upgrade-pr

Author: snyk-bot

frontend/package.json

@@ -39,7 +39,7 @@
     "eslint-plugin-prettier": "^5.0.0",
     "file-loader": "^6.0.0",
     "html-webpack-plugin": "^5.5.0",
-    "mini-css-extract-plugin": "^2.7.2",
+    "mini-css-extract-plugin": "^2.7.6",
     "node-sass": "^8.0.0",
     "prettier": "3.0.0",
     "sass-loader": "^13.1.0",