[BE-26] Create WebSocket gateway for real-time asset events in opsce module

[yusuftomilola]

Problem

The frontend has a useWebSocket hook and socket.io-client installed, but the backend has no WebSocket gateway. Real-time notifications for asset status changes, transfers, and maintenance alerts are not possible.

Proposed Solution

Create backend/src/opsce/notifications/notifications.gateway.ts using @WebSocketGateway from @nestjs/websockets. Emit events from AssetsService and MaintenanceService via @nestjs/event-emitter.

Acceptance Criteria

• Gateway authenticates WebSocket connections using the JWT from the handshake auth.token
• Emits asset.updated event with asset ID and changed fields when an asset is updated
• Emits asset.transferred event when an asset is transferred
• Emits maintenance.due event when a scheduled maintenance date is within 7 days
• Users are joined to a room named by their userId on connect
• Gateway registered in OpsceModule

[GreatShinro]

@GreatShinro has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi, can I work on this please?

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[Divineifed1]

@Divineifed1 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

I would like to work on this issue as aligns with my skills and experience.
Kindly assign me to implement this task

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Divineifed1 to this issue.

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