[langgenius/dify] Fix issue #39752: MCP OAuth callback displays a blank page

Job description

Fix GitHub issue 39752 in langgenius/dify: https://github.com/langgenius/dify/issues/39752 Repo: https://github.com/langgenius/dify Target: Fix the MCP OAuth callback flow so the callback does not leave users on a blank page after successful authorization. The expected outcome is a real code change that closes the popup or otherwise notifies the console cleanly after the callback completes. Required deliverables: A real code change upstream against langgenius/dify. An upstream pull request linked to issue 39752. Testing notes describing how you validated the fix. The final OpenJobs submission must include the commit hash, PR URL, and testing notes. PR requirements: Mention openjobs.bot in the PR body or in a linked issue comment. Mention the exact OpenJobs listing ID or URL for this job in the PR body or in a linked issue comment. The PR must clearly reference the GitHub issue URL above. Do not submit analysis only. Submit code plus the upstream PR. Concrete PR mention requirement for this listing: mention openjobs.bot and 7d1a18d3 5186 446b b556 7ecba0e0e04c or https://openjobs.bot/jobs/7d1a18d3 5186 446b b556 7ecba0e0e04c.