feat(electron): add persistent auth, auto-updater, and NAS copy script

- Integrate electron-store for persistent PocketBase auth backup
  across localStorage clears and app reinstalls
- Switch build target from portable to nsis to generate latest.yml
  for electron-updater generic provider
- Add user confirmation dialogs before download and before install
- Add post-build script to copy .exe/.yml/.nupkg to NAS share and
  local electron-update/ directory for nginx volume mount
- Mount ./electron-update into frontend nginx containers via
  docker-compose for automatic update file serving

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

electron/package.json

@@ -7,11 +7,15 @@
     "start": "electron .",
     "start:dev": "electron . --env=dev",
     "start:uat": "electron . --env=uat",
-    "build": "electron-builder --win",
-    "build:portable": "electron-builder --win portable"
+    "build": "electron-builder --win && node scripts/copy-to-nas.js",
+    "build:portable": "electron-builder --win portable && node scripts/copy-to-nas.js",
+    "copy-to-nas": "node scripts/copy-to-nas.js"
   },
   "dependencies": {
-    "electron-store": "^8.2"
+    "electron-store": "^8.2",
+    "electron-updater": "^6.8.3",
+    "png-to-ico": "^3.0.1",
+    "sharp": "^0.34.5"
   },
   "devDependencies": {
     "electron": "^35.0",
@@ -26,12 +30,24 @@
     "win": {
       "target": [
         {
-          "target": "portable",
+          "target": "nsis",
           "arch": ["x64"]
         }
       ],
       "icon": "build/icon.ico"
     },
+    "nsis": {
+      "oneClick": false,
+      "allowToChangeInstallationDirectory": true,
+      "createDesktopShortcut": true,
+      "createStartMenuShortcut": true,
+      "shortcutName": "GameGroup"
+    },
+    "publish": {
+      "provider": "generic",
+      "url": "http://nas.wjl-work.top:7034/electron-update/",
+      "channel": "latest"
+    },
     "files": [
       "main.js",
       "preload.js",