fix(desktop): report real hostname/platform/arch in heartbeat

Renderer was registering clients with navigator.platform ("MacIntel") and
a hardcoded "renderer-preview" cpu_arch. Source device info from the main
process (os.hostname + process.platform/arch) via a new device-info IPC,
and let heartbeats always send the authoritative runtime values so stale
registrations self-heal.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop-client/src/preload/bridge.ts

@@ -8,9 +8,16 @@ import type {
 } from "@geo/shared-types";
 import type { DesktopRuntimeSnapshot } from "../renderer/types";
 
+interface DesktopDeviceInfo {
+  device_name: string;
+  os: string;
+  cpu_arch: string;
+}
+
 const desktopBridge = {
   app: {
     ping: () => ipcRenderer.invoke("desktop:ping") as Promise<string>,
+    deviceInfo: () => ipcRenderer.invoke("desktop:device-info") as Promise<DesktopDeviceInfo>,
     runtimeSnapshot: () =>
       ipcRenderer.invoke("desktop:runtime-snapshot") as Promise<DesktopRuntimeSnapshot>,
     bindPublishAccount: (platformId: string) =>