[Fix] [Studio]: route cancelled oauth flows back to login page

[Gautam25Raj]

Description

When a user cancels GitHub or LinkedIn authorization, Better Auth looks for an errorCallbackURL. Because one was not passed in SocialAuth.tsx, it defaulted to ${baseURL}/error, redirecting users to the raw backend API domain (api.veriworkly.com).

This change:

• Passes an explicit errorCallbackURL pointing to ${window.location.origin}/login?error=cancelled when calling authClient.signIn.social(...).
• Checks for error query parameters on /login, shows a "Sign in was cancelled" notification, and removes the parameters from the URL bar without a page reload.

Linked Issue

Fixes #198

Type of Change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• ✨ New feature (non-breaking change which adds functionality)
• 💥 Breaking change (fix or feature that would cause existing functionality to not work as expected)
• 📝 Documentation update
• 🧪 Tests (adding or updating tests)

Checklist

• I have read the CONTRIBUTING.md document.
• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• My changes generate no new warnings.
• I have added tests that prove my fix is effective or that my feature works.
• New and existing unit tests pass locally with my changes.
• Any dependent changes have been merged and published in downstream modules.