feat: add loading state and prevent duplicate submissions

[ty-kim7]

This pull request enhances the user experience of the SQL challenge interface by improving the handling of the "Test" and "Submit" buttons to prevent duplicate submissions, provide visual feedback during operations, and ensure buttons are always re-enabled even after errors. These improvements are implemented in both the source (sql_challenge.js) and the minified/static JavaScript bundle.

User interaction improvements:

• Added logic to both executeSQLQuery and submitSQLChallenge functions to prevent duplicate clicks by disabling the respective buttons while processing and re-enabling them after completion, including in error and early-return cases. This ensures users can't accidentally submit multiple requests. [1] [2] [3] [4] [5]
• Provided loading feedback by updating button text to show a spinner and status ("Testing..." or "Submitting...") during operations, restoring the original text afterward. [1] [2] [3] [4]

Static asset update:

• Updated the minified/static JavaScript bundle (sql_challenge.1f1e9271.js) to reflect the above interaction improvements, ensuring consistent behavior in production.…llenge buttons