GitLab

The settings form contains multiple <input type="url"> fields that lack
a name attribute. When a field value fails browser URL validation, the
browser silently blocks form submission without showing an error — no
network request is made, and the user sees no feedback.

Root cause: HTML5 form validation requires a focusable element with a
name attribute to surface errors. Without it, validation fails silently.

Fix:
- Add novalidate to the <form> to disable browser-native URL validation
- Add an isValidHttpUrl() helper in saveSettings() to replicate the
  same checks the backend performs
- Optional URL fields (frontend_url, doc_url): auto-clear invalid values
  instead of blocking the save, matching backend behaviour (these fields
  accept empty string without error)
- purchase_subscription_url: block save with a clear error message when
  enabled + invalid; auto-clear when disabled to prevent the backend 400
  "Purchase Subscription URL must be an absolute http(s) URL" error
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>