Light user group and access
---------------------------

A light user is an internal user that have reduced privilege compared to a
regular user. Technically speaking, the group_user is given to the light users.
A new regular user group is added to match the old 'user' role.
(access are adapted accordingly so that the new regular group match
the old user group)

A light use have the following default groups:
- Lunch : User : Order your meal
- Attendance: User: Read his own attendances
- HR: Employee
- POS: User
A light user can see its default privileges reduced (it remains a light user)
but cannot have additional privileges. In that case, it will become a regular
user.

Light user use cases - One for each employee
--------------------------------------------

A light user is meant to be created for each employee. The HR user can create
one using the employee_user_widget or with a Invite button on the employee
form. Each employee should have at least a light user (but this is not
mandatory).

The goal is to allow each employee to have a low access user (backend)
without having to pay the full price of a regular user.

-> A post init hook have been added to create a light user for each demo
employee.

Light user lifecycle for employees
----------------------------------

A new Employee user status widget is added to the employee form view.

This widget allows the user to directly see if the employee has a user,
and what is its status. The widget allows some actions depending on the status:
- No user: create user (send invitation)
- Invited: resend invitation / deactivate / copy invitation link
- Confirmed: Deactivate / reset password
- Archived: Reactivate

When archiving the user, the end of collaboration is also called in the process,
if the employee is under contract.

Invitation Link
---------------

For now, invitation flow involves only the standard sign up link, that targets
one user at a time. Later, the invitation flow will be improved to ease the
onboarding of multiple new employee at the same time.
The final solution has not been found yet.

Task-6112938

Add support for selecting optional products after adding a product to the cart,
and introduce a shared layout for product-related pages.

### Optional product selection

Products linked through `pos_optional_product_ids` are proposed on a dedicated
optional product page after adding a product. Customers can add and configure
each suggestion, including attributes and combo choices, before continuing to
the cart.

Product selection is moved into a shared `ProductCard` component used by the
product list, combo and optional product pages. This also centralizes product
availability rules and the fly-to-cart animation.

Self-order configurability helpers are moved from `SelfOrder` to
`product.template`, and `product_name_widget` is replaced by the shared
`ProductCard`.

### Shared product page layout

The product, combo and optional product pages now use a shared
`ProductInterface` component for their common layout:

```text
+---------------------------+
|          Header           |
+---------------------------+
|                           |
|   Scrollable Content      |
|  +---------------------+  |
|  |    Name & Image     |  |
|  +---------------------+  |
|  |                     |  |
|  |   Page Content      |  |
|  |                     |  |
|  +---------------------+  |
|                           |
+---------------------------+
|          Footer           |
+---------------------------+
```

The component handles the shared header, sticky title, scroll shadow and
footer, while exposing `content`, `scroll-end-content` and `footer` slots so
each page only defines its specific content.


Task-5441062