Enables sandbox for all windows except main

ts/windows/loading/preload.ts

@@ -2,7 +2,10 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { contextBridge } from 'electron';
+import { config } from '../../context/config';
+import { localeMessages } from '../../context/localeMessages';
 
-import { SignalContext } from '../context';
-
-contextBridge.exposeInMainWorld('SignalContext', SignalContext);
+contextBridge.exposeInMainWorld('SignalContext', {
+  getI18nLocale: () => config.resolvedTranslationsLocale,
+  getI18nLocaleMessages: () => localeMessages,
+});