docs: link query optimization guide from monitoring page (#48935)

Adds a Query optimization card to the Monitoring listing on
/docs/guides/monitoring-and-debugging, pointing at
/docs/guides/database/query-optimization.

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->

## Summary by CodeRabbit

* **Documentation**
* Added a “Query optimization” entry to the telemetry monitoring
content.
* Links readers to guidance on analyzing database indexes and query
plans.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

apps/docs/data/content-listings/telemetry.data.ts

@@ -61,6 +61,11 @@ export const telemetryMonitoring: ContentListingGroup = {
       href: '/guides/monitoring-and-debugging/client-side-tracing',
       description: 'Correlate browser requests end-to-end using W3C Trace Context.',
     },
+    {
+      title: 'Query optimization',
+      href: '/guides/database/query-optimization',
+      description: 'Find and fix slow queries using indexes and query plan analysis.',
+    },
     {
       title: 'Sentry integration',
       href: '/guides/monitoring-and-debugging/sentry-monitoring',