Resolve fallback dns addrs during build

ts/types/DNSFallback.ts

@@ -0,0 +1,18 @@
+// Copyright 2024 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import z from 'zod';
+
+export const DNSFallbackSchema = z.array(
+  z.object({
+    domain: z.string(),
+    endpoints: z.array(
+      z.object({
+        family: z.enum(['ipv4', 'ipv6']),
+        address: z.string(),
+      })
+    ),
+  })
+);
+
+export type DNSFallbackType = z.infer<typeof DNSFallbackSchema>;

ts/types/RendererConfig.ts

@@ -6,6 +6,7 @@ import { z } from 'zod';
 import { Environment } from '../environment';
 import { themeSettingSchema } from './StorageUIKeys';
 import { HourCyclePreferenceSchema } from './I18N';
+import { DNSFallbackSchema } from './DNSFallback';
 
 const environmentSchema = z.nativeEnum(Environment);
 
@@ -40,6 +41,7 @@ export const rendererConfigSchema = z.object({
   contentProxyUrl: configRequiredStringSchema,
   crashDumpsPath: configRequiredStringSchema,
   ciMode: z.enum(['full', 'benchmark']).or(z.literal(false)),
+  dnsFallback: DNSFallbackSchema,
   environment: environmentSchema,
   homePath: configRequiredStringSchema,
   hostname: configRequiredStringSchema,