SD-11577: add queue health metrics

[rtalvarez]

Pull Request Template

Description

Adds the following metrics, related to queue health

• cloudflare_queue_backlog_messages: Average number of messages in queue backlog
• cloudflare_queue_backlog_bytes: Average backlog size in bytes
• cloudflare_queue_consumer_concurrency: Average number of concurrent queue consumers
• cloudflare_queue_operations_count: Number of queue message operations by action type and outcome
• cloudflare_queue_operations_bytes: Total bytes processed by queue message operations
• cloudflare_queue_operations_lag_time: Average lag time between write and read/delete (milliseconds)
• cloudflare_queue_operations_retry_count: Average retry count for queue message operations

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Code refactoring
• Other (please describe):

Testing

Ran the app locally and verified the following graphql query gets executed correctly

DEBUG[2026-03-19 11:24:33] func:main.NewGraphQLClient.func1 file:graphql.go >> query:
        query ($accountID: String!, $mintime: Time!, $maxtime: Time!, $limit: Int!) {
                viewer {
                        accounts(filter: {accountTag: $accountID}) {
                                queueBacklogAdaptiveGroups(limit: $limit, filter: {datetime_geq: $mintime, datetime_lt: $maxtime}) {
                                        dimensions {
                                                queueId
                                        }
                                        avg {
                                                messages
                                                bytes
                                        }
                                }
                                queueConsumerMetricsAdaptiveGroups(limit: $limit, filter: {datetime_geq: $mintime, datetime_lt: $maxtime}) {
                                        dimensions {
                                                queueId
                                        }
                                        avg {
                                                concurrency
                                        }
                                }
                                queueMessageOperationsAdaptiveGroups(limit: $limit, filter: {datetime_geq: $mintime, datetime_lt: $maxtime}) {
                                        dimensions {
                                                queueId
                                                actionType
                                                outcome
                                        }
                                        sum {
                                                billableOperations
                                                bytes
                                        }
                                        avg {
                                                lagTime
                                                retryCount
                                        }
                                }
                        }
                }
        }

I have also verified that the new metrics are available on localhost:8080/metrics

Code Quality

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation

Before Submitting

Please ensure you have completed the following before submitting your PR:

# Run comprehensive tests
make pr-tests

If the above command fails, please fix the issues before submitting your PR.

Additional Notes

Add any other context about the pull request here.