Add a generic module displaying the connected portal user's membership
status in the account sidebar, below the "Edit information" link.
The native Odoo membership label (``res.partner.membership_state`` from
the ``membership`` module) is shown as a colored badge:
- green (``text-bg-success``) for free / paid members;
- yellow (``text-bg-warning``) for waiting / invoiced members;
- red (``text-bg-danger``) otherwise.
Color, icon and label are computed in the QWeb template; no model or
field is added. Includes HttpCase tests covering member and non-member
rendering and asserting no action button is rendered.
