feat: multi-language support for agent search and admin pipeline config

- search_agents now accepts output_language parameter (en/zh-TW/ja)
- Admin Settings: added Pipeline Configuration section (enabled, max_concurrent_stages, default_timeout_secs)
- Admin Settings: search config now includes vlm_output_language dropdown
- Added translations for pipeline config in en/zh-TW/ja locales
- Agent search uses searchConfig.vlm_output_language for output language

src/api/index.ts

@@ -301,6 +301,7 @@ case 'search_keyword': {
     case 'search_agents': {
       const body: any = { query: a.query }
       if (a.conversationId) body.conversation_id = a.conversationId
+      if (a.outputLanguage) body.output_language = a.outputLanguage
       return { url: '/api/v1/agents/search', method: 'POST', body, timeout: 180000 }
     }