Improve HTMX error handling

[data-sync-user]

Improve behavior when HTMX requests fail or replace components that require JavaScript initialization

• Add an HTMX failure handler that reloads the page if a request fails so the UI does not remain in an inconsistent state
• Investigate CodeMirror errors after HTMX swaps?
• Make sure CodeMirror and other JavaScript-backed components are initialized correctly after HTMX updates
• Verify that components continue working after repeated swaps

┆Issue is synchronized with this Jira Task