Improve DX: warn or block invite emails when Site URL is not configured

• [ yes] I confirm I have searched the [Docs]( GitHub [Discussions]( and [Discord]( Describe the issue Invite confirmation emails fall back to localhost when Site URL is not configured . Invite confirmation emails sent from Supabase Studio can contain broken magic links that use as the base URL. This happens when the project Site URL is not configured in Authentication settings. Supabase Auth silently falls back to localhost, resulting in unusable invite links for end users. Related to #41321. To Reproduce Steps to reproduce the behavior, please provide code snippets or a repository: 1. Go to authetication, then users 2. Click on invite user 3. Type email and invite 4. After invite user 5. Check email, The link has localhost as the baseurl Actual behavior The confirmation email contains a link similar to: This link is not reachable for the invited user and results in a failed connection. Expected behavior One of the following would improve the experience: R…