feat: structured WebSocket frame view with direction, type, size and filters

[AmisKwok]

Summary / 摘要

Add a structured WebSocket frame viewer (direction, frame type, size, sent/received filters) and bump the package to 1.8.0. / 新增结构化 WebSocket 帧视图（方向、帧类型、大小、收发筛选），并将包版本提升至 1.8.0。

Changes / 变更

• Add a structured WebSocket frame list to the network detail view with sent/received filtering and auto-scroll, replacing the flat text blob. / 在网络详情中以结构化 WebSocket 帧列表（收发筛选、自动滚动）替代原纯文本块。
• Extend WsFrame with frame type (text/binary/close) and byte size; expose frames via WsInspectorService.framesFor with lazy eviction of trimmed sessions. / 为 WsFrame 增加帧类型与字节大小，并通过 WsInspectorService.framesFor 暴露，对裁剪会话做惰性淘汰。
• Add unit tests for WsInspectorService and dartdoc for the new public API. / 为 WsInspectorService 增加单元测试并补充新增公共 API 的 dartdoc。
• Bump version to 1.8.0 across pubspec.yaml, ios/zero_inspector_kit.podspec, README, CHANGELOG and the docs site. / 在 pubspec.yaml、podspec、README、CHANGELOG 及文档站同步版本至 1.8.0。
• Add missing dartdoc to WidgetTreeService.isEnabled. / 为 WidgetTreeService.isEnabled 补充缺失的 dartdoc。

Context / 背景

WebSocket traffic was previously shown as an unusable flat text blob in the network inspector; this makes individual frames inspectable by direction, type and size. / 此前网络检查器里的 WebSocket 流量只是难以阅读的纯文本块，本次改动让每帧可按方向、类型、大小查看。

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

• Run flutter test and confirm ws_inspector_service_test passes. / 运行 flutter test 确认 ws_inspector_service_test 通过。
• Open the network detail of a captured WebSocket and verify the frame list, filters and auto-scroll. / 打开被捕获 WebSocket 的网络详情，验证帧列表、筛选与自动滚动。

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