feat(server-config): restart required toast (#7479)

## Summary

Show a warning toast when leaving Server Config with pending changes,
reminding users they must restart to apply changes.

## Changes

- **What**: Add a `onBeforeUnmount` toast in `ServerConfigPanel` when
`modifiedConfigs` is non-empty and the user didn’t click Restart; add
i18n strings.

## Review Focus

- Confirm the toast timing/conditions are correct (only fires on leaving
the panel; suppressed when Restart is clicked).

> [!NOTE]
> This is a stacked PR. (main <=
https://github.com/Comfy-Org/ComfyUI_frontend/pull/7478 <=
https://github.com/Comfy-Org/ComfyUI_frontend/pull/7479)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7479-feat-server-config-restart-required-toast-2ca6d73d3650811f85f7f0c52c4cf8f0)
by [Unito](https://www.unito.io)

src/locales/en/main.json

@@ -631,7 +631,9 @@
   "serverConfig": {
     "modifiedConfigs": "You have modified the following server configurations. Restart to apply changes.",
     "revertChanges": "Revert Changes",
-    "restart": "Restart"
+    "restart": "Restart",
+    "restartRequiredToastSummary": "Restart required",
+    "restartRequiredToastDetail": "Restart the app to apply server configuration changes."
   },
   "shape": {
     "default": "Default",
@@ -2450,4 +2452,4 @@
     "recentReleases": "Recent releases",
     "helpCenterMenu": "Help Center Menu"
   }
-}
+}