feat(plugins): show plugin logs on detail page via Docs/Logs tablist

Add a Logs tab beside Documentation on the plugin detail page, showing
the output a plugin prints through the standard Python logger (per the
wiki style guide). Logs are captured from the plugin's stderr by the
plugin runtime and fetched on demand.

- Bump langbot-plugin pin to 0.4.4 (adds GET_PLUGIN_LOGS action)
- plugin_connector/handler: get_plugin_logs RPC client
- HTTP route GET /api/v1/plugins/<author>/<name>/logs (limit + level)
- Frontend: wrap detail right panel in Docs/Logs Tabs; PluginLogs
  component with level filter, manual + 3s auto refresh, bottom-follow
- i18n: 7 new keys across all 8 locales

web/src/i18n/locales/zh-Hans.ts

@@ -552,6 +552,13 @@ const zhHans = {
     viewSource: '查看来源',
     loadingReadme: '正在加载文档...',
     noReadme: '该插件没有提供 README 文档',
+    tabDocs: '文档',
+    tabLogs: '日志',
+    logsLevelAll: '全部级别',
+    logsRefresh: '刷新',
+    logsAutoRefreshOn: '自动刷新：开',
+    logsAutoRefreshOff: '自动刷新：关',
+    logsEmpty: '暂无日志。插件通过 logger 打印的日志会显示在这里。',
     fileUpload: {
       tooLarge: '文件大小超过 10MB 限制',
       success: '文件上传成功',