[BE-23] Implement CSV and Excel asset export with ExcelJS in opsce module

[yusuftomilola]

Problem

Asset managers need to export data for reporting and offline analysis. exceljs and json2csv are installed but no export endpoints exist.

Proposed Solution

Create backend/src/opsce/exports/exports.service.ts and backend/src/opsce/exports/exports.controller.ts. Support CSV and XLSX formats with the same filter parameters as GET /api/assets.

Acceptance Criteria

• GET /api/assets/export?format=csv returns a downloadable .csv file
• GET /api/assets/export?format=xlsx returns a downloadable .xlsx file
• Exported columns: ID, Name, Category, Status, Condition, Serial Number, Department, Location, Assigned To, Purchase Date, Purchase Value, Current Value
• Accepts the same filter query params as the assets list endpoint (status, category, departmentId, etc.)
• Response sets Content-Disposition: attachment; filename=assets-export-{date}.csv
• Returns 400 if format is not csv or xlsx

[Amas-01]

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Hello Maintainer
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[feyishola]

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Hi im Feyishola a software developer with over 4 years of experience. Please let me handle this issue

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[Menjay7]

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Hi! I’m a full-stack developer with a strong blockchain background. I’d love to handle this issue and I will deliver a clean, reliable solution. Kindly assign it to me.

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[whisper011]

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Gm! I'd like to work on this.

I've gone through the issue and understand what needs to be done. I'll keep the fix scoped, clean, and tested — and communicate clearly if anything comes up along the way.

Ready to start immediately. Feel free to assign it!

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[drips-wave]

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[drips-wave]

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

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