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/en.json

@@ -139,6 +139,13 @@
             "missingPath": "Set a download location before downloading example images.",
             "unavailable": "Example image downloads aren't available yet. Try again after the page finishes loading."
         },
+        "checkModelUpdates": {
+            "label": "Check for updates",
+            "loading": "Checking for {type} updates...",
+            "success": "Found {count} update(s) for {type}s",
+            "none": "All {type}s are up to date",
+            "error": "Failed to check for {type} updates: {message}"
+        },
         "cleanupExampleImages": {
             "label": "Clean up example image folders",
             "success": "Moved {count} folder(s) to the deleted folder",