Raise the webhook limit per workspace (currently: 1)

Currently only one webhook URL can be configured per Senja project. This means users are limited to a single automated flow triggered from Senja — any new automation requires overwriting the existing webhook URL.

Even a modest increase (10–20 slots) would unblock most real-world use cases: separate flows for new testimonials, published testimonials, testimonial requests, etc.

This is independent from the programmatic API request — even with manual configuration, the single-slot limit is a hard constraint for anyone building more than one automation.