feat(crm): invoice update notes and PO fields

Allow oo invoices update --description/--po so Notizen can be
multiline refs without portal URLs; keep opportunity link support.

cmd/oo/invoices.go

@@ -160,13 +160,14 @@ Example:
 
 func invoiceUpdateCmd() *cobra.Command {
 	var opportunityID int64
+	var description, po string
 	cmd := &cobra.Command{
 		Use:   "update INVOICE_ID",
-		Short: "Update invoice (link to opportunity)",
+		Short: "Update invoice (opportunity link, notes, PO)",
 		Args:  cobra.ExactArgs(1),
 		RunE: func(cmd *cobra.Command, args []string) error {
-			if opportunityID == 0 {
+			if opportunityID == 0 && !cmd.Flags().Changed("description") && !cmd.Flags().Changed("po") {
-				return fmt.Errorf("--opportunity is required")
+				return fmt.Errorf("set --opportunity and/or --description and/or --po")
 			}
 			c, err := newOO(cmd)
 			if err != nil {
@@ -175,6 +176,10 @@ func invoiceUpdateCmd() *cobra.Command {
 			out, err := c.UpdateInvoice(cmd.Context(), args[0], onlyoffice.UpdateInvoiceParams{
 				EntityID:         opportunityID,
 				EntityType:       0,
+				Description:      description,
+				DescriptionSet:   cmd.Flags().Changed("description"),
+				PurchaseOrder:    po,
+				PurchaseOrderSet: cmd.Flags().Changed("po"),
 			})
 			if err != nil {
 				return err
@@ -184,6 +189,8 @@ func invoiceUpdateCmd() *cobra.Command {
 		},
 	}
 	cmd.Flags().Int64Var(&opportunityID, "opportunity", 0, "CRM opportunity/deal id to link")
+	cmd.Flags().StringVar(&description, "description", "", "invoice notes (Notizen); use \\n for line breaks")
+	cmd.Flags().StringVar(&po, "po", "", "purchase order number")
 	return cmd
 }
 

invoices.go

@@ -115,11 +115,15 @@ func (c *Client) CreateInvoice(ctx context.Context, p CreateInvoiceParams) (map[
 }
 
 // UpdateInvoiceParams are fields for PUT /api/2.0/crm/invoice/{id}.
-// Loads the current invoice and merges non-zero entity / contact updates.
+// Loads the current invoice and merges non-zero / set fields.
 type UpdateInvoiceParams struct {
 	EntityID        int64 // link to opportunity; 0 = leave unchanged
 	EntityType      int
 	ContactID       int64  // 0 = leave unchanged
+	Description     string // invoice notes; empty + DescriptionSet=false keeps existing
+	DescriptionSet  bool
+	PurchaseOrder   string
+	PurchaseOrderSet bool
 }
 
 // UpdateInvoice PUTs a full invoice body (OnlyOffice requires complete payload).
@@ -196,6 +200,12 @@ func (c *Client) UpdateInvoice(ctx context.Context, id string, p UpdateInvoicePa
 		"status":              statusID,
 		"invoiceLines":        lines,
 	}
+	if p.DescriptionSet {
+		body["description"] = p.Description
+	}
+	if p.PurchaseOrderSet {
+		body["purchaseOrderNumber"] = p.PurchaseOrder
+	}
 	if p.EntityID != 0 {
 		body["entityId"] = p.EntityID
 		body["entityType"] = p.EntityType