Queue/Metrics utilization dashboard for usage overview

Clear and concise description of the problem

Currently, tracking usage pattern is hard for admins as there is no easy way to get queue statistics over time. The API endpoint queue/info provides some basic stats but one would need to query it every few seconds/minute and then post-process the data manually into a dashboard.

Yes, there is a prometheus endpoint at /metrics and some user-provided dasbhoard (e.g. https://github.com/Janik-Haag/woodpecker-grafana-dashboard) but having a built-in view would be really great.

Suggested solution

Add a simple dashboard to admin#queue which shows queue utilization over time.

Bonus: group the stats by agent (e.g. to infer how many builds for a given architecture were requested)

https://github.com/arl/statsviz might be a library for this.

Alternative

No response

Additional context

No response

Validations

• Checked that the feature isn't part of the next version already [https://woodpecker-ci.org/faq#which-version-of-woodpecker-should-i-use]
• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that request the same feature to avoid creating a duplicate.