feat: support configuring default server URL for desktop (#7363)

packages/app/src/context/platform.tsx

@@ -37,6 +37,12 @@ export type Platform = {
 
   /** Fetch override */
   fetch?: typeof fetch
+
+  /** Get the configured default server URL (desktop only) */
+  getDefaultServerUrl?(): Promise<string | null>
+
+  /** Set the default server URL to use on app startup (desktop only) */
+  setDefaultServerUrl?(url: string | null): Promise<void>
 }
 
 export const { use: usePlatform, provider: PlatformProvider } = createSimpleContext({