[feature] "Delete all watches" button

Would be nice to have a "Delete all watches" aswell as "Delete all Groups" buttons

Start by locating the existing "Delete all Groups" button and its handler, then trace how watch deletion is currently performed. Add an equivalent button for deleting all watches, confirm the action's behavior matches the existing group deletion flow, and run the relevant tests or manual UI checks available in the project.

Written by the indexing model from the issue text.