Fix ES module error - use CommonJS for main process

- Removed 'type: module' from package.json
- Added postbuild script to create CommonJS package.json in dist/main
- Fixed main entry path

build-output/win-unpacked/portable.txt

@@ -1 +1 @@
-Portable Mode Enabled
+Portable Mode

package.json

@@ -2,14 +2,14 @@
   "name": "ip-monitor",
   "version": "1.0.0",
   "description": "Modern IP Monitor Desktop Application",
-  "main": "dist/main/main/index.js",
+  "main": "dist/main/index.js",
-  "type": "module",
   "scripts": {
     "dev": "concurrently \"npm run dev:vite\" \"npm run dev:electron\"",
     "dev:vite": "vite",
     "dev:electron": "wait-on tcp:5173 && cross-env NODE_ENV=development electron .",
-    "build": "npm run build:main && npm run build:renderer",
+    "build": "npm run build:main && npm run build:renderer && npm run postbuild",
     "build:main": "tsc -p tsconfig.main.json",
+    "postbuild": "echo {\"type\":\"commonjs\"} > dist/main/package.json",
     "build:renderer": "vite build",
     "build:electron": "npm run build && electron-builder --win",
     "build:portable": "npm run build && electron-builder --win portable",