frontend: pin source-map to 0.7.4

0.7.6 makes problems.

Author: BacLuc

frontend/package-lock.json

@@ -113,6 +113,7 @@
     "lint-staged": "16.1.4",
     "prettier": "3.6.2",
     "sass": "1.78.0",
+    "source-map": "0.7.4",
     "unplugin-vue-components": "28.8.0",
     "vite": "6.3.5",
     "vite-plugin-comlink": "5.1.0",