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/en-US.ts

@@ -577,6 +577,14 @@ const enUS = {
     viewSource: 'View Source',
     loadingReadme: 'Loading documentation...',
     noReadme: 'This plugin does not provide README documentation',
+    tabDocs: 'Documentation',
+    tabLogs: 'Logs',
+    logsLevelAll: 'All levels',
+    logsRefresh: 'Refresh',
+    logsAutoRefreshOn: 'Auto-refresh: On',
+    logsAutoRefreshOff: 'Auto-refresh: Off',
+    logsEmpty:
+      'No logs yet. Logs printed by the plugin via logger will appear here.',
     fileUpload: {
       tooLarge: 'File size exceeds 10MB limit',
       success: 'File uploaded successfully',