Depreciate Asset

Post ONE period's depreciation for one asset (the manual per-asset door).

Single-period by design: the orchestrator posts due depreciation in bulk, and this is the accountant's manual override for one asset and one period.

Refusals are 422. One carries a machine-readable code: the period already has a depreciation entry for this asset — conflict.assetAlreadyDepreciated, safe to treat as "already done" rather than as a failure, since each period is depreciated exactly once (a reversed depreciation releases its period). The date rules carry codes too: conflict.assetNotYetInUse (the period ends before the month the asset is ready for use — that month is the first one depreciated), conflict.assetPeriodNotStarted (no depreciation for months still ahead), conflict.assetAcquisitionReversed (the asset's acquisition entry was reversed) and conflict.assetRegisterOutOfSync. The others are prose only: the asset is deactivated for the period's fiscal year (reactivate it in the year-end fixed-asset review first), and the posting date falls outside the period or in a closed period or sealed year. 404 for an unknown asset.

journal_entry_id comes back null, with a 200, when the run was a no-op: the asset is no longer active, or its depreciable base is exhausted (which flips it to fully_depreciated). Check it rather than assuming a posting. A period that already has an entry is the one no-op that answers 422 instead, because it is the one a caller must be able to recognise.