[BE-28] Implement depreciation engine — straight-line and declining-balance schedules

[yusuftomilola]

Overview

Assets carry purchasePrice, purchaseDate, and currentValue, but nothing computes depreciation — the #1 feature finance teams expect from an asset register (Snipe-IT, Asset Panda, and every ITAM tool ship it). Charts are planned as [FE-23].

What to Build

A DepreciationModule in backend/src/depreciation/:

1. Asset entity additions (coordinate with [BE-06]/[BE-14]): depreciationMethod (enum NONE | STRAIGHT_LINE | DECLINING_BALANCE), usefulLifeMonths, salvageValue
2. DepreciationService:
   • getSchedule(assetId) → array of { period, openingValue, depreciation, closingValue } over the useful life
   • getCurrentBookValue(assetId) → value as of today
3. Endpoints:

Method	Path	Description
GET	/api/assets/:id/depreciation	Full schedule + current book value
GET	/api/reports/depreciation	Org-wide: total book value, monthly depreciation expense, top depreciating categories

4. Nightly cron updates currentValue from the schedule for assets with a method set

References

• Blocked by [BE-06], [BE-14]; feeds [FE-23] and extends [BE-13]

Acceptance Criteria

• Straight-line: (cost − salvage) / usefulLifeMonths per month, verified against a hand-computed example in the issue/PR description
• Declining-balance implemented with a configurable rate
• Book value never drops below salvage value
• Schedule endpoint returns correct values for assets purchased mid-month and fully-depreciated assets
• Org-wide report aggregates in SQL where possible

[Olo2u]

@Olo2u has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi Maintainer, I’ve taken little time to go through the issue and I understand what needs to be done. The task aligns well with my skills, and I’d be happy to take responsibility for implementing the fix and making sure it meets the stated requirements. I’m willing to get started if you’re okay with assigning it to me.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Olo2u to this issue.

[RennyThompson]

@RennyThompson has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I'd like to take this on.

Assets carry purchasePrice, purchaseDate, and currentValue, but nothing computes depreciation — the #1 feature finance teams expect from an asset register (Snipe-IT, Asset Panda, and every ITAM tool ship it). Charts are planned as [FE-23].

I'll make sure each of these is covered:

• Straight-line: (cost − salvage) / usefulLifeMonths per month, verified against a hand-computed example in the issue/PR description
• Declining-balance implemented with a configurable rate
• Book value never drops below salvage value
• Schedule endpoint returns correct values for assets purchased mid-month and fully-depreciated assets

I'll keep you posted on progress as I go.

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

[drips-wave]

Congratulations, @RennyThompson! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @RennyThompson: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox!

@RennyThompson's PR #1358 was approved and merged by @yusuftomilola.

🏆 @RennyThompson: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (363 total points). Track your full progress on GrantFox.

👏 Great work, @RennyThompson! Keep contributing to DistinctCodes.

[drips-wave]

This issue has been completed by @RennyThompson as part of the Stellar Wave Program's 8th Wave 🥳

😎 @RennyThompson: You earned 200 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here. You can also Leave a review to share your experience working on this issue.

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