docs: add Workers VPC metrics and settings dashboard changelog entry

Author: thomasgauvin

src/assets/images/changelog/workers-vpc/2026-03-12-metrics-dashboard.png

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+---
+title: Observability for Workers VPC Services
+description: Debug and monitor your private network connections with per-service metrics, error breakdowns, and latency tracking.
+date: 2026-03-12
+---
+
+Each VPC Service now has a **Metrics** tab so you can monitor connection health and debug failures without leaving the dashboard.
+
+![Workers VPC Metrics dashboard showing connections, latency, and errors charts](~/assets/images/changelog/workers-vpc/2026-03-12-metrics-dashboard.png)
+
+- **Connections** — See successful and failed connections over time, broken down by who is responsible: your origin (Bad Upstream), your configuration (Client), or Cloudflare (Internal).
+- **Latency** — Track connection and DNS resolution latency trends.
+- **Errors** — Drill into specific error codes grouped by category, with filters to isolate upstream, client, or internal failures.
+
+A new **Settings** tab lets you view and edit service configuration, host details, and port assignments in one place.
+
+![Workers VPC Settings dashboard showing service, host, and port configuration](~/assets/images/changelog/workers-vpc/2026-03-12-settings-dashboard.png)
+
+For a full list of error codes and what they mean, refer to [Troubleshooting](/workers-vpc/reference/troubleshooting/).