Unread message counts in Odoo’s enterprise mail experience are now tracked at the conversation channel level rather than on the broader thread object. This makes the mail interface’s unread indicators more consistent and easier to maintain, with minimal direct impact on day-to-day users.

Community: odoo/odoo#98149
Part of task-2948676.

This update keeps the Documents kanban view aligned with the latest interface styling changes. It removes a duplicated styling setting and adjusts the layout so the view continues to display correctly after the broader design refresh.

Part of the overall v16 SCSS optimization/restyle, task-2704984

Requires: 
- https://github.com/odoo/odoo/pull/96195

task-2892062

New automated performance checks were added for key Knowledge navigation paths. These tests help monitor database usage when users open the Knowledge tree panel or main Knowledge menu, supporting future optimization work without changing user-facing behavior.

This commit simply introduces a query counter test for the tree panel knowledge
route. This will allow us to optimize that route in following commits.

While we are at it, we also add a quick query counter test for the
'action_home_page' method, as it is called every time the main Knowledge menu
is clicked.

Task-2791000