Configure Prometheus to write to Mimir when Mimir is enabled

As a developer, I want to connect Grafana Mimir with our Prometheus data sources to centralize metrics collection and storage:

Acceptance Criteria:

• Configure Mimir to pull metrics from Prometheus and Metrics Server
• Verify that Mimir is storing metrics in a format compatible with Prometheus queries
• Test basic query operations to ensure data accuracy and availability

Note: Requires big-bang/apps/sandbox/mimir#27 to validate metrics with Grafana dashboard