Create company documents from uploaded files

Turns files the caller has uploaded into company documents, filed on companyId (default: the caller's own company), which must be in the caller's network — else 404. shareWithCompanyId, also in the network, auto-approves a share of every new document with that company. The caller becomes the owner. Files the caller did not upload are skipped rather than failing the batch, so the response can hold fewer documents than were sent, or none. isPublic is honoured as sent. Responds 201 with the stored documents as a bare array, not wrapped in { data, metadata }: both frontends read it that way. fileUrl is a read-only signed link valid for an hour and originalFileUrl is the storage key. Publishes a created event per document, and a cascade-tracing event when any is of a node-mapping type.