Vercel template deployments now trigger automatically

When users create a project from a Vercel template through the marketplace, they previously needed to manually trigger the first deployment after connecting GitHub. This PR automates that step.

A new triggerInitialDeployment function was added to the platform service that calls Vercel's API to start a production deployment. The GitHub connection route now checks if the request originated from a marketplace flow — identified by an origin=marketplace parameter — and automatically triggers the initial deployment once GitHub is connected.

The Vercel onboarding modal was updated to pass this origin parameter when launched from marketplace context, and the form schema was extended to capture it. Additionally, several error-level log messages were downgraded to warnings where the conditions represent expected validation failures rather than system errors.

This change lives in the webapp services and routes handling Vercel integration, completing the end-to-end template deployment flow for Vercel marketplace users.