Add loader on OAuth2 consent page submit

[gearnode]

Summary

On the OAuth2 consent page, clicking Allow or Deny now shows a loading spinner on the clicked button while the mutation runs. After a successful response, the form is replaced with a full-page redirect screen that names the application and shows a spinner while the browser navigates to the OAuth callback URL. This prevents double submits and gives clearer feedback during slow redirects.

Changes

• Track a pendingAction state while the mutation is in flight; disable both buttons and show a spinner on the active one
• After success with a redirectURL, show a full-page state:
  • Allow: "Authorization Complete" + "You will be redirected to {app name}…"
  • Deny: "Access Denied" + "You will be redirected to {app name}…"
• Navigate to the callback URL via useEffect once the redirect screen is shown
• Reset pending state only on mutation errors

Test plan

• Open the OAuth2 consent page (/auth/consent?consent_id=…)
• Click Allow — spinner on Allow during mutation, then redirect screen with app name
• Confirm redirect completes without duplicate consent submissions
• Click Deny — spinner on Deny during mutation, then redirect screen with app name
• Simulate a mutation error — buttons re-enable and toast is shown

Linear Issue: ENG-579

  

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Summary by cubic

Adds a loading state and a post-submit redirect screen to the OAuth2 consent page. Meets Linear ENG-579 by preventing double submits and showing clear feedback during the OAuth redirect.

App: console +51 -9

• Track pendingAction to block repeat clicks and disable both buttons
• Show per-button loading spinners; keep until redirect
• After success, replace form with a spinner redirect screen naming the app; navigate via window.location in useEffect
• Reset pending only on errors; remove isInFlight

^{Written for commit f9f1ce5. Summary will update on new commits.}