Deepen all business modules: methods, validations, workflows

Account:
- action_post: partner validation, line count check, sequence number
  assignment (JOURNAL/YYYY/NNNN format)
- action_register_payment: opens payment wizard from invoice
- remove_move_reconcile: undo reconciliation, reset residuals
- Register Payment button in invoice form (visible when posted+unpaid)

Sale:
- action_cancel: cancels linked draft invoices + SO state
- action_draft: reset cancelled SO to draft
- action_view_invoice: navigate to linked invoices
- Cancel/Reset buttons in form view header

Purchase:
- button_draft: reset cancelled PO to draft
- action_create_bill already existed

Stock:
- action_cancel on picking: cancels moves + picking state

CRM:
- action_set_won_rainbowman: sets Won stage + rainbow effect
- convert_opportunity: lead→opportunity type switch

HR:
- hr.contract model (name, employee, wage, dates, state)

Project:
- action_blocked on task (kanban_state)
- Task stage seed data (New, In Progress, Done, Cancelled)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

addons/sale/models/sale_order.go

@@ -584,6 +584,68 @@ func initSaleOrder() {
 		}, nil
 	})
 
+	// action_cancel: Cancel a sale order and linked draft invoices.
+	// Mirrors: odoo/addons/sale/models/sale_order.py SaleOrder.action_cancel()
+	m.RegisterMethod("action_cancel", func(rs *orm.Recordset, args ...interface{}) (interface{}, error) {
+		env := rs.Env()
+		for _, soID := range rs.IDs() {
+			// Cancel linked draft invoices
+			rows, _ := env.Tx().Query(env.Ctx(),
+				`SELECT id FROM account_move WHERE invoice_origin = (SELECT name FROM sale_order WHERE id = $1) AND state = 'draft'`, soID)
+			for rows.Next() {
+				var invID int64
+				rows.Scan(&invID)
+				env.Tx().Exec(env.Ctx(), `UPDATE account_move SET state = 'cancel' WHERE id = $1`, invID)
+			}
+			rows.Close()
+			env.Tx().Exec(env.Ctx(), `UPDATE sale_order SET state = 'cancel' WHERE id = $1`, soID)
+		}
+		return true, nil
+	})
+
+	// action_draft: Reset a cancelled sale order back to quotation.
+	// Mirrors: odoo/addons/sale/models/sale_order.py SaleOrder.action_draft()
+	m.RegisterMethod("action_draft", func(rs *orm.Recordset, args ...interface{}) (interface{}, error) {
+		env := rs.Env()
+		for _, soID := range rs.IDs() {
+			env.Tx().Exec(env.Ctx(), `UPDATE sale_order SET state = 'draft' WHERE id = $1 AND state = 'cancel'`, soID)
+		}
+		return true, nil
+	})
+
+	// action_view_invoice: Open invoices linked to this sale order.
+	// Mirrors: odoo/addons/sale/models/sale_order.py SaleOrder.action_view_invoice()
+	m.RegisterMethod("action_view_invoice", func(rs *orm.Recordset, args ...interface{}) (interface{}, error) {
+		env := rs.Env()
+		soID := rs.IDs()[0]
+		var soName string
+		env.Tx().QueryRow(env.Ctx(), `SELECT name FROM sale_order WHERE id = $1`, soID).Scan(&soName)
+
+		// Find invoices linked to this SO
+		rows, _ := env.Tx().Query(env.Ctx(),
+			`SELECT id FROM account_move WHERE invoice_origin = $1`, soName)
+		var invIDs []interface{}
+		for rows.Next() {
+			var id int64
+			rows.Scan(&id)
+			invIDs = append(invIDs, id)
+		}
+		rows.Close()
+
+		if len(invIDs) == 1 {
+			return map[string]interface{}{
+				"type": "ir.actions.act_window", "res_model": "account.move",
+				"res_id": invIDs[0], "view_mode": "form",
+				"views": [][]interface{}{{nil, "form"}}, "target": "current",
+			}, nil
+		}
+		return map[string]interface{}{
+			"type": "ir.actions.act_window", "res_model": "account.move",
+			"view_mode": "list,form", "views": [][]interface{}{{nil, "list"}, {nil, "form"}},
+			"domain": []interface{}{[]interface{}{"id", "in", invIDs}}, "target": "current",
+		}, nil
+	})
+
 	// action_create_delivery: Generate a stock picking (delivery) from a confirmed sale order.
 	// Mirrors: odoo/addons/sale/models/sale_order.py SaleOrder._action_confirm() → _create_picking()
 	m.RegisterMethod("action_create_delivery", func(rs *orm.Recordset, args ...interface{}) (interface{}, error) {