fix: accepted status codes custom range discarded on tag creation

[AmanUllah687]

Summary

In this pull request, the following changes are made:

• Added a missing @tag handler to the Accepted Status Codes multiselect
  in the HTTP(s), Globalping, and Websocket Upgrade monitor forms. The
  field was marked taggable but had no @tag listener, so pressing Enter
  on a custom range like 200-399 cleared the input instead of adding it
  as a tag.
• Added a new addAcceptedStatusCode method, following the same pattern
  already used in this file for addKafkaProducerBroker and
  addRabbitmqNode.
• The server already validates these ranges correctly in
  checkStatusCode() (server/util-server.js), so this was purely a
  frontend gap. No backend changes needed.

• Resolves Accepted Status Codes custom range is discarded despite “create a tag” prompt #7684

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. N/A, this only adds a missing listener, no existing behavior changes.
• 🧠 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. No new UI, just wiring an existing field.
• 🛠️ 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). N/A, the added method is a one-line push matching the existing sibling methods, no comment needed for consistency.
• 🤖 I added or updated automated tests where appropriate. N/A, no existing test coverage for the sibling handlers either.
• 📄 Documentation updates are included (if applicable). N/A.
• 🧰 Dependency updates are listed and explained. N/A.
• ⚠️ CI passes and is green.

accepted-status-code-tag-fix-demo.mp4.mp4

[github-actions]

Thanks for the PR! If anyone would like to help with testing, run: npx kuma-pr AmanUllah687:fix-accepted-status-code-tag (requires Node.js and Docker)

[AmanUllah687]

The failing check (auto-test windows-latest, 20) is SystemServiceMonitorType > check() returns UP for a running service, which fails because the Dnscache Windows service isn't running/found on that CI runner. This is unrelated to my change, EditMonitor.vue isn't touched by that test at all, and it passes on windows-latest, Node 24 and every other OS/Node combination.