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/views/SearchView.vue

@@ -815,6 +815,7 @@ async function sendMessage() {
       const res: any = await apiCall('search_agents', {
         query: q,
         conversationId: conversationId.value || null,
+        outputLanguage: searchConfig.value.vlm_output_language || 'en',
       })
       if (searchSeq !== seq) return
       if (res?.conversation_id) conversationId.value = res.conversation_id