Add talk to schedule directly from browse sessions list

It would be useful to be able to add a session to your own schedule from the list of sessions shown when tapping on the "browse sessions" button without having to open the session details page.

Feedback from @samynomad and @JonasHelming.

Start at the screen opened by the "browse sessions" button and compare it with the session details page, where adding a session to the personal schedule is already available. Trace how the browse list renders sessions and how the schedule action is triggered; done means a session can be added directly from that list without opening its details.

Written by the indexing model from the issue text.