[Feature] Timeout should be only a (signed) positive integer

[Geolim4]

Is your feature request related to a problem? Please describe.
The configurable timeout should be a positive integer only in the admin form.

Describe the solution you'd like
Add a Symfony constraint to disallow "-n" numbers.

Describe alternatives you've considered
N/A

Additional context
A customer I had with access admin to its shop has modified by mistake (mouse scroll on page scroll) the timeout and it was set to -3. Symony process crashed for days because the timeout value was invalid (obviously).