🧪 Add test for create_page API error path

[yj9404]

🎯 What: Added a unit test to verify the create_page function correctly handles unexpected API errors (e.g. non-400 failure status codes).

📊 Coverage: Covered the error path in create_page when the Confluence API responds with a non-400 status. The test verifies that requests.exceptions.HTTPError is raised in this scenario.

✨ Result: Improved test coverage and assurance that exceptions are properly bubbled up for API failures.

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PR created automatically by Jules for task 3406718721330680398 started by @yj9404

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