Adds a "Cards" tab to the Profile Background picker (BackgroundsView)
that selects a pattern applied to the entire user info card and the
extended profile container, in addition to the existing avatar-pad
background/stand/overlay layers.
- AvatarInfoUser/Utilities: propagate cardBackgroundId from RoomUserData.
- InfoStandWidgetUserView: stateful cardBackgroundId, applied as
.profile-card-background.card-background-{id} on the outer Column
with bg-color suppressed when active.
- UserContainerView: same class on the wrapper of the extended profile.
- BackgroundsView: 4th tab "cards" backed by cards.data config
(falls back to backgrounds.data); sends 4-id message via the
extended sendBackgroundMessage signature.
- ui-config.example: cards.data dataset (15 entries).
- BackgroundsView.css: 188 .card-background-{N} rules cloned from
background-{N} (repeat-tiled) plus 15 CSS-pattern overrides for the
provisional dataset (gradients, stripes, dots, grid, checker).
duckietm