Switch Elsa Studio workflow execution from /execute to async /dispatch

**Description**

_Currently, Elsa Studio_
triggers workflows using the synchronous /execute endpoint. This causes the client to wait for workflow completion and can lead to blocking behavior, timeouts, or poor UX for long-running workflows.

It would be useful if Elsa Studio could optionally use the asynchronous /dispatch endpoint instead, allowing workflows to be scheduled and executed in the background.

_Expected behavior_

- Elsa Studio should support triggering workflows through /dispatch.
- Ideally this could be:

- configurable globally, or
- selectable per workflow/action.

- The UI should handle async execution gracefully:

- return workflow instance ID,
- optionally poll for status,
- or provide navigation to the running workflow instance.

**Motivation**

_Using /dispatch would:_

- avoid blocking HTTP requests,
- improve handling of long-running workflows,
- reduce timeout-related failures,
- better support distributed/background execution scenarios.