feat: add model updates check to global context menu

Add a new "Check Model Updates" option to the global context menu that allows users to manually check for model updates. This includes:

- Adding refreshUpdates endpoint to API configuration
- Implementing checkModelUpdates method with proper loading states
- Adding internationalization support for update messages
- Handling success/error states with appropriate user feedback
- Automatically reloading models after update check completes

The feature provides users with manual control over update checks and improves visibility into model update availability.

locales/zh-TW.json

@@ -139,6 +139,13 @@
             "missingPath": "請先設定下載位置再下載範例圖片。",
             "unavailable": "範例圖片下載目前尚不可用。請在頁面載入完成後再試一次。"
         },
+        "checkModelUpdates": {
+            "label": "檢查更新",
+            "loading": "正在檢查 {type} 更新...",
+            "success": "找到 {count} 個 {type} 更新",
+            "none": "所有 {type} 都是最新版本",
+            "error": "檢查 {type} 更新失敗：{message}"
+        },
         "cleanupExampleImages": {
             "label": "清理範例圖片資料夾",
             "success": "已將 {count} 個資料夾移至已刪除資料夾",