feat: add Performance Tracing Oven

[alowpoly]

Summary

• add the built-in Performance Tracing Oven with strict retained-report and source-provenance validation
• reject stale reports with HTTP 409 when measured inputs change
• adapt timing history and frame samples into the shared dashboard renderer
• load the Performance Tracing Oven's own declarative layout and repo-scoped data

Verification

• npm run build:dashboard
• npm run test:performance-tracing
• npm run verify
• npm run verify:package