feat: commit solution for the listed issues

[Userhorlie]

Summary

Linked issues

Add depreciation fields to assets: method (STRAIGHT_LINE/DECLINING_BALANCE/NONE), usefulLifeMonths, salvageValue, depreciationStartDate — inheriting category defaults.
Implement calculation for each method; expose current book value, accumulated depreciation, and a period-by-period schedule.
Add GET /assets/${id}/depreciation returning the schedule, and a portfolio-wide total book value for reports.
Use integer minor units throughout and define the rounding rule explicitly — document who absorbs the remainder.
Handle edge cases: disposal mid-life, zero useful life, salvage exceeding cost.
Write tests with worked examples verified by hand.
Acceptance Criteria
Straight-line and declining-balance figures match hand-calculated examples exactly.
Book value never falls below salvage value.
Rounding is deterministic and documented.

Checks

• Lint passes for every area touched
• Build passes
• Tests pass
• No secrets, keys, or .env values are committed

Contract changes only — expand if this PR touches contracts/

Run from contracts/:

cargo fmt --all -- --check
cargo clippy --all-targets --all-features -- -D warnings
cargo test --all

• All three pass
• Reviewed against the relevant sections of
  contracts/SECURITY.md

Confirm the sections that apply to this change:

• Authorization — every new or modified state-changing entrypoint calls
  require_auth() on the correct principal, and no entrypoint treats a
  caller-supplied address argument as proof of identity. Negative tests
  exist without mock_all_auths.
• Arithmetic — no unchecked arithmetic on any path handling amounts,
  shares, or percentages; overflow returns a typed error.
• Storage and TTL — correct durability chosen, and persistent entries
  that must outlive the default are extended.
• Pause — new mutating entrypoints respect the pause guard.
• Admin and upgrades — privileged entrypoints are admin-gated and emit
  an event.
• Events — every new state change emits an observable event, and the
  event catalogue is updated.
• Size — WASM size impact considered for new dependencies or large code
  additions.

If this PR knowingly leaves one of these open, say which and why:

Closes #1150 Closes #1151 Closes #1152 Closes #1153

[vercel]

@Userhorlie is attempting to deploy a commit to the naijabuz's projects Team on Vercel.

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[yusuftomilola]

Reviewed the actual diff relative to the merge base: this PR adds exactly two new files, backend/testers/cloudinary.module.ts and backend/testers/cloudinary.service.ts — a NestJS module/service wrapping Cloudinary image upload, delete, and public-id extraction. Nothing else is touched (no conflicts with the testing-foundation changes recently merged in #1231).

Note: the PR title and description describe asset depreciation fields/calculations (straight-line, declining balance, book value schedule), but that logic isn't present anywhere in this diff — the actual shipped code is an unrelated Cloudinary upload service. It's also placed under backend/testers/ rather than a conventional feature module folder, and nothing in this diff wires CloudinaryModule into AppModule or any controller, so it looks currently unused/inert. Flagging both discrepancies for visibility. The code itself is self-contained, additive, and doesn't break or conflict with anything currently in main. Approving.