Add vendor publish to document system

Replace the old snapshot-based system for vendors with the publish
document system, mirroring the prior processing activity / DPIA / TIA
migration. Includes the GraphQL mutation, MCP tool, CLI command, n8n
operation, frontend publish dialog, e2e tests, and a prosemirror
register template covering vendor profile fields plus per-vendor
sections for services, contacts, risk assessments, compliance reports,
BAA and DPA agreements.

The vendor register lives as a generated DocumentTypeRegister document
on the organization, reused across publishes (the major version bumps
on every republish). Approvers can be passed in to create a draft
pending approval; otherwise the version is published immediately. The
frontend Vendors page exposes a Publish button and a Document link
button when the document exists, and pre-fills the previous default
approvers.

Remove snapshot mode entirely from vendors and their sub-entities: drop
snapshotId/sourceId from GraphQL Vendor type and VendorFilter; remove
SnapshotsTypeVendors from the snapshot registry and delete
Vendors.Snapshot, VendorSnapshotter interface and all
*.InsertVendorSnapshots methods on contacts, services, risk
assessments, compliance reports, BAA and DPA. Drop the snapshot routes
and banner from the frontend. The snapshot_id columns remain in the
database but are now filtered out with snapshot_id IS NULL.

Add Get/Upsert/Clear GeneratedDocumentID methods on Vendor backed by a
new vendors_document_id column on generated_documents, matching the
ProcessingActivity/Finding/Obligation pattern.

Signed-off-by: Sacha Al Himdani <sacha@getprobo.com>

pkg/coredata/migrations/20260428T152537Z.sql

@@ -0,0 +1,16 @@
+-- Copyright (c) 2026 Probo Inc <hello@getprobo.com>.
+--
+-- Permission to use, copy, modify, and/or distribute this software for any
+-- purpose with or without fee is hereby granted, provided that the above
+-- copyright notice and this permission notice appear in all copies.
+--
+-- THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH
+-- REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
+-- AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT,
+-- INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
+-- LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
+-- OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+-- PERFORMANCE OF THIS SOFTWARE.
+
+ALTER TABLE generated_documents
+    ADD COLUMN vendors_document_id TEXT REFERENCES documents(id) ON DELETE SET NULL;