Prometheus exporter redo v16 branch

[mitchross]

Redo of -> #5594
Addresses #2266

Proposed change

This PR adds comprehensive Prometheus metrics support to Frigate, enabling better monitoring and observability of the system. The integration:

• Exposes a /metrics endpoint in Prometheus format
• Leverages existing stats collection system
• Provides detailed metrics for:
  • Camera performance (FPS, detection rates)
  • System resources (CPU, memory, GPU usage)
  • Storage utilization
  • Detection performance
  • Service health metrics
  • Temperature monitoring

This will allow users to:

• Monitor Frigate performance using industry-standard tools
• Create custom dashboards in Grafana
• Set up alerts based on metrics
• Track long-term performance trends

The implementation piggybacks on the existing stats collection system, ensuring minimal overhead while providing valuable monitoring capabilities.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code
• Documentation Update

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• The code has been formatted using Ruff (ruff format frigate)

Additional Notes:

• The implementation uses the official prometheus_client library
• Metrics follow Prometheus naming conventions
• No breaking changes to existing functionality
• Minimal performance impact as it uses existing stats collection
• All metrics are properly documented with descriptions
• Labels are used consistently for better querying

[mitchross]

@hawkeye217 @NickM-27 @blakeblackshear - redid the branch

[hawkeye217]

Looks good, thanks!

[jangrewe]

Thanks @mitchross! ♥️