refactor(hub): rename Device ID to Hub ID in console layer

Rename the business-layer concept from "Device ID" to "Hub ID" for
better user comprehension. The underlying network transport layer
still uses deviceId — Hub ID is passed as the deviceId value.

- Rename device.ts → hub-identity.ts, getDeviceId → getHubId
- Storage file: ~/.super-multica/device-id → ~/.super-multica/hub-id
- Hub property: deviceId → hubId
- API response field: deviceId → hubId
- Console UI label: "Device ID" → "Hub ID"

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/console/app.controller.ts

@@ -17,7 +17,7 @@ export class AppController {
   @Get("hub")
   getHub() {
     return {
-      deviceId: this.hub.deviceId,
+      hubId: this.hub.hubId,
       url: this.hub.url,
       connectionState: this.hub.connectionState,
       agentCount: this.hub.listAgents().length,