feat: 全平台打包 + CI/CD 自动构建工作流

- 修复移动端: axios替换为原生fetch (React Native兼容)
- 新增 .gitea/workflows/build.yml CI/CD工作流:
  - Windows: NSIS安装包 (windows-latest)
  - macOS: DMG x64+arm64 (macos-latest)
  - Linux: AppImage+deb (ubuntu-latest)
  - Android: APK via expo prebuild + gradle (ubuntu-latest)
  - iOS: simulator build (macos-latest)
  - 移动端JS Bundle导出 (android+ios)
  - 自动创建Release (tag触发)

本地已构建产物:
- client/release/FunConnect-1.1.0-Win-x64.exe (73MB)
- client/release/FunConnect-1.1.0-Linux-x64.zip (99MB)
- mobile JS bundles (android + ios) 已验证导出成功

mobile/.gitignore

@@ -1,6 +1,7 @@
 node_modules/
 .expo/
 dist/
+release/
 *.jks
 *.p8
 *.p12