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/scripts/copy-to-nas.js

@@ -0,0 +1,63 @@
+const fs = require('fs')
+const path = require('path')
+
+const srcDir = path.join(__dirname, '..', 'dist')
+// 项目根目录下的 electron-update，用于 docker volume 挂载给 nginx
+const localUpdateDir = path.join(__dirname, '..', '..', 'electron-update')
+// NAS 共享路径
+const nasDir = '\\\\JIULUGNAS\\personal_folder\\CodeSpace\\GameGroup2'
+
+function ensureDir(dir) {
+  try {
+    if (!fs.existsSync(dir)) {
+      fs.mkdirSync(dir, { recursive: true })
+    }
+    return true
+  } catch (err) {
+    console.error(`[copy-to-nas] failed to create dir ${dir}:`, err.message)
+    return false
+  }
+}
+
+function copyFilesTo(destDir, label) {
+  if (!fs.existsSync(srcDir)) {
+    console.log(`[copy-to-nas] dist not found, skipping ${label}`)
+    return
+  }
+
+  const files = fs.readdirSync(srcDir).filter((f) => {
+    // 只复制更新相关文件：安装包、yml、blockmap、nupkg
+    const ext = path.extname(f).toLowerCase()
+    return (
+      ext === '.exe' ||
+      ext === '.yml' ||
+      ext === '.blockmap' ||
+      ext === '.nupkg' ||
+      ext === '.yaml'
+    )
+  })
+
+  if (files.length === 0) {
+    console.log(`[copy-to-nas] no update files found in dist, skipping ${label}`)
+    return
+  }
+
+  if (!ensureDir(destDir)) return
+
+  for (const file of files) {
+    const src = path.join(srcDir, file)
+    const dest = path.join(destDir, file)
+    try {
+      fs.copyFileSync(src, dest)
+      console.log(`[copy-to-nas] copied ${file} -> ${destDir}`)
+    } catch (err) {
+      console.error(`[copy-to-nas] failed to copy ${file} to ${label}:`, err.message)
+    }
+  }
+}
+
+// 复制到本地目录（供 docker volume 挂载）
+copyFilesTo(localUpdateDir, 'local')
+
+// 复制到 NAS
+copyFilesTo(nasDir, 'NAS')