monitor.js throws redeclaration error after AJAX reload

[godmafiaze]

Describe the bug
The Monitor page can reload content using AJAX. When monitor.js is executed more than once, top-level let and const declarations can throw a JavaScript redeclaration error.

Example browser console error:

Uncaught SyntaxError: Identifier 'refreshMSeconds' has already been declared

This can prevent Monitor dropdowns and filter controls from applying changes correctly after an AJAX reload.

To Reproduce
Steps to reproduce the behavior:

1. Go to the Monitor tab.
2. Change a Monitor filter/dropdown such as View, Size, or Refresh.
3. Let the Monitor page reload content through AJAX.
4. Check the browser console.
5. The redeclaration error may appear and subsequent dropdown/filter changes may stop applying.

Expected behavior
The Monitor page JavaScript should be safe to execute after AJAX reloads, and Monitor dropdown/filter controls should continue working.

Screenshots
A browser console screenshot can be provided if needed.

Plugin (please complete the following information):

• Version: develop branch
• Source: github
• Identifier: Cacti/plugin_monitor develop branch

Desktop (please complete the following information):

• OS: Windows 11 / Rocky Linux server
• Browser: Chrome
• Version: latest available version

Smartphone (please complete the following information):

• Device: N/A
• OS: N/A
• Browser: N/A
• Version: N/A

Additional context
The issue appears to be caused by top-level let and const declarations in js/monitor.js.

Changing the top-level declarations to var avoids redeclaration errors when the script is executed again during AJAX reloads.