fix: Toolbar when maxHistory is set to 0

[michalsn]

Description
This PR fixes issues with the debug bar when maxHistory is set to 0:

• A JavaScript error occurred because the expected button does not exist.
• Debug toolbar history files were not properly cleaned up.

Fixes #9504

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[neznaika0]

All good, but HTMX creates an unlimited number of json files until a new HTTP request is executed (example F5 in browser).

[michalsn]

IMO, this is fine as-is. The limit should only apply to "normal" requests (when we actually display the toolbar). Otherwise, we’d introduce a much bigger problem: removing a debug entry from history would be possible even though it’s still visible in the list of available data. Let’s avoid complicating things unnecessarily.

If you're using the codeigniter-htmx library, you should not experience this problem since the debug toolbar is reloaded on every request.

[michalsn]

Thank you @paulbalandan and @neznaika0