[BE-35] Add Resource Usage Tracker service for per-session consumption logging

[devwums]

Problem

Per-session resource consumption (printing credits, internet data, locker usage) has no tracking mechanism. Resource abuse goes undetected.

Proposed Solution

Create backend/cntr/resource-usage.service.ts exporting: ResourceType union ('PRINT' | 'INTERNET' | 'LOCKER'), ResourceUsageLog interface ({ sessionId, memberId, resourceType: ResourceType, quantity: number, unit: string, recordedAt: string }), and createUsageLog(sessionId: string, memberId: string, resourceType: ResourceType, quantity: number, unit: string): ResourceUsageLog. Throws RangeError if quantity <= 0. All implementation must live inside backend/cntr/.

Acceptance Criteria

• File at backend/cntr/resource-usage.service.ts
• recordedAt is new Date().toISOString()
• Throws RangeError for quantity <= 0
• Exports ResourceType union and ResourceUsageLog interface
• Unit test at backend/cntr/resource-usage.service.spec.ts

[Thommyy7]

@Thommyy7 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hello maintainers,

I’m interested in contributing to this issue.

I have experience working with Rust and enjoy contributing to open-source projects. I’ve reviewed the task and feel comfortable implementing the required changes while keeping the solution aligned with the project's existing structure and standards.

If the issue is still available, I’d appreciate being considered for assignment.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Thommyy7 to this issue.

[drips-wave]

Congratulations, @Thommyy7! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

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[drips-wave]

This issue has been completed by @Thommyy7 as part of the Stellar Wave Program's 5th Wave 🥳

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