[ADD] zero_stock_approval: create module and implement approval logic

[pkhu-odoo]

Task Description -

1. Add a new Boolean field zero_stock_approval in the Sales Order form view.
2. The field should be read-only for Sales Users and editable only by the Administrator (or Sales Manager).
3. If zero_stock_approval is enabled, the user should be allowed to confirm the quotation regardless of product stock availability.
4. If zero_stock_approval is disabled, the system should prevent confirmation of the quotation when the available quantity is less than the ordered quantity.

• Created new module zero_stock_approval with required base files
• Inherited sale.order model and added zero_stock_approval field
• Overridden action_confirm method to apply custom business logic
• Extended view_order_form to include the new approval field

Task-5929841

[robodoo]