chore: bump version to 1.7.1

[AmisKwok]

Summary / 摘要

Release 1.7.1 — terminal-grade UI redesign, README language-switch spacing fix, and a network list item rendering fix. / 发布 1.7.1：终端级 UI 重做、README 语言切换间距修复，以及 Network 列表项渲染修复。

Changes / 变更

• Bump package to 1.7.1 (pubspec.yaml, ios/zero_inspector_kit.podspec, README install snippets, CHANGELOG). / 版本升至 1.7.1，同步更新安装片段与 CHANGELOG。
• Redesign the inspector theme to a terminal/developer-tool grade look — neutral graphite base + single Teal accent, 1px borders — applied across all viewers. / 主题重做为终端级风格：中性石墨灰 + 单一 Teal 强调色，1px 边框，覆盖全部 viewer。
• Fix README / README_zh language-switch header spacing (wider gap, smaller mascot icons, padded language labels). / 修复 README 语言切换头部间距，图标与语言选项不再贴在一起。
• Fix Network list items rendering empty by reverting the list item border to Border.all. / 将 Network 列表项边框还原为 Border.all，修复内容不可见问题。
• Refresh all README screenshots under image/screenshot/. / 更新 README 全部截图。

Context / 背景

Prepared the 1.7.1 release with a cleaner, terminal-grade visual language and documentation polish; also resolved a regression where network list items rendered without content. / 为 1.7.1 做准备，采用更干净的终端级视觉语言并完善文档；同时修复了 Network 列表项空白的回退问题。

Checklist / 检查项

• Title follows Conventional Commits / 标题符合约定式提交
• CI checks pass after merge / 合入后 CI 通过

Test plan

• flutter analyze and flutter test pass / 运行 flutter analyze 与 flutter test
• Run the example app, open the Network tab, and confirm request items show method / URL / status / host / 运行 example，打开 Network 标签，确认请求项显示方法、URL、状态码、host
• Verify README install snippet points to ^1.7.1 / 确认 README 安装片段指向 ^1.7.1

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