feat: 完善多账号连接诊断与聊天媒体导出

- 新增微信账号发现、环境诊断和分步数据库连接引导
- 支持按账号安全保存数据库密钥及快速切换账号
- 完善 WCDB 历史消息分片读取和分页状态提示
- 支持导出图片、视频和语音，提供原图优先及缩略图回退
- 更新安装指引、兼容版本说明和相关自动化测试

src/main/services/connection-diagnostics.ts

@@ -0,0 +1,69 @@
+import { execFile } from 'child_process'
+import fs from 'fs-extra'
+import os from 'os'
+import path from 'path'
+import { promisify } from 'util'
+import { isUsableDbRoot } from './settings-store'
+
+const execFileAsync = promisify(execFile)
+
+const platformLabel = (): string => {
+  if (process.platform === 'win32') return `Windows ${os.release()} (${process.arch})`
+  if (process.platform === 'darwin') return `macOS ${os.release()} (${process.arch})`
+  return `${process.platform} ${os.release()} (${process.arch})`
+}
+
+async function detectWindowsWechatVersion(): Promise<string> {
+  const script = [
+    '$process = Get-Process Weixin,WeChat -ErrorAction SilentlyContinue | Where-Object Path | Select-Object -First 1',
+    '$candidate = if ($process) { $process.Path } else {',
+    "  @($env:ProgramFiles, ${env:ProgramFiles(x86)}) | Where-Object { $_ } | ForEach-Object { Join-Path $_ 'Tencent\\WeChat\\WeChat.exe' } | Where-Object { Test-Path $_ } | Select-Object -First 1",
+    '}',
+    'if ($candidate) { (Get-Item -LiteralPath $candidate).VersionInfo.ProductVersion }'
+  ].join('; ')
+  try {
+    const { stdout } = await execFileAsync(
+      'powershell.exe',
+      ['-NoProfile', '-NonInteractive', '-Command', script],
+      { timeout: 3000, windowsHide: true }
+    )
+    return stdout.trim() || '未检测到'
+  } catch {
+    return '未检测到'
+  }
+}
+
+async function detectMacWechatVersion(): Promise<string> {
+  const candidates = [
+    '/Applications/WeChat.app/Contents/Info',
+    path.join(os.homedir(), 'Applications/WeChat.app/Contents/Info')
+  ]
+  for (const candidate of candidates) {
+    if (!fs.existsSync(`${candidate}.plist`)) continue
+    try {
+      const { stdout } = await execFileAsync(
+        '/usr/bin/defaults',
+        ['read', candidate, 'CFBundleShortVersionString'],
+        { timeout: 3000 }
+      )
+      if (stdout.trim()) return stdout.trim()
+    } catch {
+      // Continue to the next known installation location.
+    }
+  }
+  return '未检测到'
+}
+
+export async function detectWechatVersion(): Promise<string> {
+  if (process.platform === 'win32') return detectWindowsWechatVersion()
+  if (process.platform === 'darwin') return detectMacWechatVersion()
+  return '未检测到'
+}
+
+export function detectDataStructureVersion(dbRoot: string): string {
+  return isUsableDbRoot(dbRoot) ? '微信 4.x（WCDB）' : '未检测到'
+}
+
+export function getOsVersionLabel(): string {
+  return platformLabel()
+}