fix: group reordering causes incorrect expansion state of adjacent groups when pausing/resuming

[speedcoder430]

Summary

In this pull request, the following changes are made:

• Changed :key="index" to :key="item.id" in MonitorListItem.vue child group rendering, because using array index as the Vue :key caused component instances to retain stale isCollapsed state when the sorted list reordered after pausing/resuming a group.

• Fixed the IPv6 bracket-stripping test in test-util-server.js to handle environments where IPv6 is reachable, because assert.rejects fails when the ping succeeds.

• Resolves Group reordering causes incorrect expansion state of adjacent groups when pausing/resuming #6781

Please follow this checklist to avoid unnecessary back and forth (click to expand)

• ⚠️ If there are Breaking change (a fix or feature that alters existing functionality in a way that could cause issues) I have called them out
• 🧠 I have disclosed any use of LLMs/AI in this contribution and reviewed all generated content.
  I understand that I am responsible for and able to explain every line of code I submit.
• 🔍 Any UI changes adhere to visual style of this project.
• 🛠️ I have self-reviewed and self-tested my code to ensure it works as expected.
• 📝 I have commented my code, especially in hard-to-understand areas (e.g., using JSDoc for methods).
• 🤖 I added or updated automated tests where appropriate.
• 📄 Documentation updates are included (if applicable).
• 🧰 Dependency updates are listed and explained.
• ⚠️ CI passes and is green.

Screenshots for Visual Changes

N/A — no visual changes. The fix is a :key binding correction that preserves existing UI behavior (group expansion state stays with the correct group during list reordering).

[github-actions]

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[CommanderStorm]

Change LGTM, will need to manually test this though before merging.

Could you fix the linting error?

[speedcoder430]

Change LGTM, will need to manually test this though before merging.

Could you fix the linting error?

Hi @CommanderStorm , Thanks for your kind feedback. I fixed the linting error. Please review the code on your end again. Thanks