Reindex resource when link status changes

[fbacall]

Summary of changes

• Trigger a reindex of an event/material if its URL is detected as being broken (or back online)

Motivation and context

Resources with dead links were showing up in search results due to not being indexed after the link monitor updated.

Checklist

• I have read and followed the CONTRIBUTING guide.
• I confirm that I have the authority necessary to make this contribution on behalf of its copyright owner and agree
  to license it to the TeSS codebase under the
  BSD license.

[Copilot]

Pull Request Overview

This PR adds functionality to automatically reindex search resources when their link status changes between working and broken states. This ensures that resources with dead links are properly excluded from search results and resources that come back online are re-included.

• Adds a status_changed? method to detect transitions between working and failing link states
• Implements automatic reindexing via an after_commit callback when link status changes
• Includes comprehensive test coverage for the status change detection logic

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
app/models/link_monitor.rb	Adds status change detection and automatic reindexing callback
test/models/link_monitor_test.rb	Adds test coverage for the new status change detection method

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