The activity menu test has been relocated into the test mail area so it can use a more suitable real test model. This is an internal cleanup that prepares future testing changes without affecting end users.

In preparation for the adaptation of its test adaptation, the `systray_activity_menu_test` is moved to test_mail. Indeed,
with this adaptation, all fake models will be replaced by real ones, the `MailTestActivity` model is the perfect candidate for this..

task-2792108

The export dialog’s visual styling has been cleaned up to make the interface easier to maintain. This is an internal refactor with minimal expected impact for users, while helping future updates be delivered more consistently.

This commit simplifies the SCSS of the export dialog.

task-2816763

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This update simplifies the styling behind the mobile messaging navigation bar as part of Odoo's broader interface restyling work. It should make the mobile messaging area easier to maintain while preserving the user experience.

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

task-2837311

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The mail app’s video call configuration menu styling was simplified as part of a broader interface cleanup. This keeps the underlying design easier to maintain and improves compatibility for users on Safari-based browsers.

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

task-2853292

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The Mail emoji picker styling was simplified as part of a broader interface cleanup. Emoji spacing was adjusted to make selecting emojis easier, improving usability with minimal functional impact.

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

This commit also uses padding instead of margin to select emojis more
easily.

task-2856230

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This update simplifies the styling of discussion previews in Odoo's Mail app as part of a broader interface cleanup. It should help keep the messaging interface consistent and easier to maintain, with little to no change in daily workflows.

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

task-2843449

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The Mail welcome screen styling was reviewed and simplified as part of a broader Odoo 16 visual optimization effort. This helps keep the interface easier to maintain while preserving the user experience.

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

task-2852562

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This update simplifies the styling and tidies the structure of the mail call layout menu. It supports ongoing interface cleanup work, making the code easier to maintain without changing business workflows.

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

task-2855553

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The Discuss area styling was simplified by replacing custom style rules with standard shared layout classes. This reduces maintenance overhead and may slightly improve page performance without changing how users work with Discuss.

Current SCSS is replaced with global Bootstrap classes, in
order to reduce code lines and to increase performance.

Task-2821258

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This update replaces a custom layout helper in the Mail app with a standard Bootstrap styling class. It keeps the messaging interface behavior consistent while reducing custom code that must be maintained over time.

This commit deletes the class `o-autogrow` and replaces each instance of
it with a global Bootstrap class.

Task-2833725

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