chore: move business tooling out of the public library; tidy filestore naming

Keep the public tree project-generic. Business/one-off tools, deployment
and business docs move to the private oo-workspace repo.

Moved to oo-workspace:
- cmd/ooscan, cmd/pdfamount, cmd/kontoblatt, cmd/kontolink
- internal/xlspipe (cutover-portugal workbook) -> oow workbook build
  (drops the --template/--title flags from oo docs put-xlsx)
- deploy/docker-compose.rclone-webdav.yml + docs/rclone-webdav.md
- docs/crm-associations.md

Removed GitHub-era leftovers:
- .github/workflows/release-please.yml, release-please-config.json,
  .release-please-manifest.json (tags are created on Gitea per SemVer)

Naming: the FileStore subsystem is now filestore_*.go (was file_*.go) to
match files_*.go (project Documents). Docs/AGENTS/README updated.

invoices.go

@@ -131,7 +131,7 @@ type UpdateInvoiceParams struct {
 // UpdateInvoice PUTs a full invoice body (OnlyOffice requires complete payload).
 //
 // Linking an opportunity via EntityID on an existing invoice often returns HTTP 400
-// on this portal — prefer CreateInvoice with EntityID set. See docs/crm-associations.md.
+// on this portal — prefer CreateInvoice with EntityID set. See the CRM association rules.
 func (c *Client) UpdateInvoice(ctx context.Context, id string, p UpdateInvoiceParams) (map[string]any, error) {
 	inv, err := c.GetInvoice(ctx, id)
 	if err != nil {
@@ -249,7 +249,7 @@ const (
 
 // SetInvoiceStatus sets CRM invoice status for one or more invoice ids
 // (PUT /api/2.0/crm/invoice/status/{statusId} with invoiceids).
-// Note: Billed→Draft often does not stick; recreate Draft instead (see docs/crm-associations.md).
+// Note: Billed→Draft often does not stick; recreate Draft instead (see the CRM association rules).
 func (c *Client) SetInvoiceStatus(ctx context.Context, statusID int, invoiceIDs ...int64) (map[string]any, error) {
 	if statusID <= 0 {
 		return nil, fmt.Errorf("status id is required")