[FIX] web: click/studio work in colored kanban tile

When a colored kanban tile is colored, and there is a color attribute on
the tile HTML element indicating a color field (eg. when a kanban view
with color dropdown is created in studio), there was a HTML element over
the whole tile preventing to click on links or other sub element of it.

This HTML element is just a transparent used for accessibility to
contain the tile color intelligible name, so this commit just size it
over the area of the color (currently in base bootstrap ~3px at the left
of the tile).

opw-1932283
closes #30717

addons/web/static/src/scss/kanban_view.scss

@@ -564,6 +564,8 @@
     @include o-kanban-record-color;
 
     .oe_kanban_color_help {
-        @include o-position-absolute(0, 5px, 0, -1px);
+        @include o-position-absolute(0, auto, 0, -1px);
+        width: $o-kanban-color-border-width;
+        z-index: 1; // show the title over kanban color
     }
 }