build: add Windows portable EXE packaging scripts

- scripts/build-icon.js — generates icon.png/ico/tray-icon.png
  from pure Node.js (no dependencies, zlib + PNG/ICO encoder)
- scripts/fix-wincodeSign.js — pre-populates electron-builder
  winCodeSign cache by extracting the .7z while ignoring macOS
  symlinks (which fail on Windows without SeCreateSymbolicLink)
- package.json: add fix-wincodeSign script, cross-env, electron-builder
  downgraded to v24 (stable portable target), CSC signing disabled

Build: npm run build:win → dist-electron/SRT-Streamer-Portable-1.0.0.exe

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

package.json

@@ -5,10 +5,12 @@
   "main": "electron/main.js",
   "scripts": {
     "dev": "concurrently \"vite\" \"wait-on http://localhost:5173 && electron .\"",
-    "build": "vite build && electron-builder",
-    "build:win": "vite build && electron-builder --win",
-    "build:mac": "vite build && electron-builder --mac",
-    "build:linux": "vite build && electron-builder --linux",
+    "icon": "node scripts/build-icon.js",
+    "build": "node scripts/build-icon.js && vite build && electron-builder",
+    "fix-wincodeSign": "node scripts/fix-wincodeSign.js",
+    "build:win": "node scripts/build-icon.js && vite build && node scripts/fix-wincodeSign.js && cross-env CSC_IDENTITY_AUTO_DISCOVERY=false electron-builder --win portable",
+    "build:mac": "node scripts/build-icon.js && vite build && electron-builder --mac",
+    "build:linux": "node scripts/build-icon.js && vite build && electron-builder --linux",
     "preview": "vite preview"
   },
   "dependencies": {
@@ -17,8 +19,9 @@
   "devDependencies": {
     "@vitejs/plugin-react": "^4.3.4",
     "concurrently": "^9.1.2",
+    "cross-env": "^7.0.3",
     "electron": "^33.4.0",
-    "electron-builder": "^25.1.8",
+    "electron-builder": "^24.13.3",
     "react": "^18.3.1",
     "react-dom": "^18.3.1",
     "vite": "^6.0.7",
@@ -28,24 +31,42 @@
   "build": {
     "appId": "com.srtstreamer.app",
     "productName": "SRT Streamer",
+    "copyright": "SRT Streamer",
     "directories": {
-      "output": "dist-electron"
+      "output": "dist-electron",
+      "buildResources": "assets"
     },
     "files": [
       "dist/**/*",
       "electron/**/*",
-      "assets/**/*"
+      "assets/**/*",
+      "package.json"
     ],
     "extraResources": [
       {
         "from": "ffmpeg-bin/",
         "to": "ffmpeg-bin/",
-        "filter": ["**/*"]
+        "filter": [
+          "**/*"
+        ]
       }
     ],
+    "asar": true,
     "win": {
-      "target": "portable",
-      "icon": "assets/icon.ico"
+      "target": [
+        {
+          "target": "portable",
+          "arch": [
+            "x64"
+          ]
+        }
+      ],
+      "icon": "assets/icon.ico",
+      "artifactName": "SRT-Streamer-Portable-${version}.exe",
+      "requestedExecutionLevel": "asInvoker",
+      "sign": null,
+      "signingHashAlgorithms": null,
+      "certificateFile": null
     },
     "mac": {
       "target": "dmg",