Label Prometheus metrics by workflow name

[cnicolov]

Summary

• Adds a backend aggregation for workflow run counts grouped by workflow name and status.
• Emits workflow_name alongside status on openworkflow_workflow_runs Prometheus samples.
• Updates dashboard/backend tests and Prometheus docs for the new label.

Verification

• npx npm@11.8.0 run format
• npm_config_engine_strict=false npx npm@11.8.0 run build
• npm_config_engine_strict=false npx npm@11.8.0 run typecheck
• npm_config_engine_strict=false npx npm@11.8.0 run lint
• npm_config_engine_strict=false npx npm@11.8.0 run knip
• npm_config_engine_strict=false npx npm@11.8.0 run lint:duplication
• npm_config_engine_strict=false npx npm@11.8.0 run test:coverage

Notes

• npm_config_engine_strict=false was needed locally because cspell declares Node >=22.18.0 while this machine has Node 22.16.0.
• npm run lint:spell could not run locally for the same Node version reason.