A keyed upload that matched a stored document by its bytes never recorded
its key, so deleting that document let the next import run store it again.
Such keys are now kept as aliases of the document, the source-key check
reads them, and the purge carries them into the ledger with the row's own.
A source key may ride the query string and is then answered before the
body is read or the hourly allowance charged; an upload answered as a
duplicate hands its slot back. GET /api/documents/inbound/source answers
whether a key is held, under the same documents:write scope, so an
importer can skip a download.
aiRead=defer is stored on the row. The summary catch-up, the summary job
and lab auto-staging skip such documents until an explicit Read with AI
or Generate summary clears the marker; backup and restore carry it.
A documents:write caller no longer sees the quota figures on a full vault.
Refs #1038
A narrow `documents:write` token, minted cookie-only at
`POST /api/tokens/documents` and accepted by the vault upload route alone.
A scoped caller draws on its own hourly bucket per token
(`DOCUMENT_UPLOAD_LIMIT_PER_HOUR`, default 120) and gets a receipt
`{ id, duplicate }` instead of the stored row.
Uploads take optional `sourceSystem` / `sourceId` fields. The source key is
unique per account across live and deleted documents, and the tombstone
purge carries it to a small ledger, so re-sending a document the owner
deleted answers 200 `deleted: true` and stores nothing. `aiRead=defer`
indexes locally and skips the summary and lab staging.
The detail sheet shows where an imported document came from; backup and
restore carry both fields; Delete All Data clears the ledger.
Refs #1038, #938
Marc-André Bombeck