Centralize Electron entry file path configuration

This commit refactors configuration to use centrally defined Electron
entry file path to improve maintainability and reduce duplication.

- Replace the hardcoded file path in the `main` field of `package.json`
  with a reference to the `ELECTRON_ENTRY` environment variable, managed
  by `electron-vite`.
- Update `electron-vite` to version 1.0.28, enabling the use of
  `ELECTRON_ENTRY` environment variable feature (details in
  alex8088/electron-vite#270).

package.json

@@ -6,7 +6,6 @@
   "description": "Enforce privacy & security best-practices on Windows, macOS and Linux, because privacy is sexy 🍑🍆",
   "author": "undergroundwires",
   "type": "module",
-  "main": "./dist-electron-unbundled/main/index.cjs",
   "scripts": {
     "dev": "vite",
     "build": "vue-tsc --noEmit && vite build",
@@ -63,7 +62,7 @@
     "electron-builder": "^24.6.4",
     "electron-devtools-installer": "^3.2.0",
     "electron-icon-builder": "^2.0.1",
-    "electron-vite": "^1.0.27",
+    "electron-vite": "^1.0.28",
     "eslint": "^8.51.0",
     "eslint-plugin-cypress": "^2.15.1",
     "eslint-plugin-vue": "^9.17.0",