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/locales/zh-TW.json

@@ -448,6 +448,26 @@
     "stat": {
       "users": "用戶",
       "shares": "共享"
+    },
+    "vlm": {
+      "minScore": "VLM 最低分數",
+      "maxResults": "VLM 最大結果數",
+      "outputLanguage": "輸出語言",
+      "hint": {
+        "minScore": "VLM 搜尋的最低相似度分數",
+        "maxResults": "VLM 搜尋的最大結果數量",
+        "outputLanguage": "VLM 描述的語言"
+      }
+    },
+    "pipeline": {
+      "enabled": "啟用",
+      "maxConcurrentStages": "最大並行階段數",
+      "defaultTimeoutSecs": "預設超時（秒）",
+      "hint": {
+        "enabled": "啟用管線處理",
+        "maxConcurrentStages": "同時執行的最大階段數",
+        "defaultTimeoutSecs": "管線執行的預設超時時間"
+      }
     }
   },
   "app": {