fix: force UI to use IPv4 (127.0.0.1) for API endpoints

Previously, the API endpoint was defined using `localhost`, which could resolve to the IPv6 address `::1`.
This caused issues because the Portmaster core service is listening on `127.0.0.1:817` and only fast-tracking connections to that specific IPv4 address.

desktop/tauri/src-tauri/capabilities/default.json

@@ -8,7 +8,7 @@
   ],
   "remote": {
     "urls": [
-      "http://localhost:817"
+      "http://127.0.0.1:817"
     ]
   },
   "permissions": [