[IMP] mail: increase systray message dropdown menu height

The goal of this task to increase the height of the systray message dropdown
to simply allow more messages to be displayed at once for better readability.

Currently, we can see a maximum of 6 chat listing in the dropdown at once and
then need to scroll down for more chats to be listed
but with this commit, We can see more number of chats based on the viewport
height for better readability.

Task : 2428779

closes odoo/odoo#66432

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/static/src/components/messaging_menu/messaging_menu.scss

@@ -29,7 +29,14 @@
         flex: 0 1 auto;
         width: 350px;
         min-height: 50px;
-        max-height: 400px;
+        /**
+        * Note: Min() refers to CSS min() and not SCSS min().
+        *
+        * We want CSS min() and not SCSS min() because the former supports calc while the latter doesn't.
+        * To by-pass SCSS min() shadowing CSS min(), we rely on SCSS being case-sensitive while CSS isn't.
+        * As a result, Min() is ignored by SCSS while CSS interprets as its min() function.
+        */
+        max-height: Min(calc(100vh - 140px), 630px);
         z-index: 1100; // on top of chat windows
     }