Add keyboard navigation for account device list

Enter/Return/Menu: open device menu
Space: toggle check device
Escape: uncheck all
Alt+R/F5: refresh device list
Alt+S/Delete: sign out checked or all sessions

src/backend/user_files.py

@@ -337,6 +337,9 @@ class UISettings(JSONDataFile):
                 "forgetRoom":                  ["Alt+Shift+Escape"],
 
                 "toggleFocusRoomPane": ["Alt+R"],
+
+                "refreshDevices":             ["Alt+R", "F5"],
+                "signOutCheckedOrAllDevices": ["Alt+S", "Delete"],
             },
         }