feat(enterprise): proxy trace processor leases

[Gracker]

Summary

• Add backend trace processor lease proxy endpoints: POST /api/tp/:leaseId/status, POST /api/tp/:leaseId/query, and raw WebSocket upgrade handling for /api/tp/:leaseId/websocket.
• Route enterprise uploads through lease-scoped HttpRpcTarget objects so Perfetto UI can use the backend proxy instead of exposing direct trace processor ports.
• Return leaseId / leaseState from backend trace uploads and persist pending backend trace state by lease when applicable.
• Refresh the committed frontend bundle to frontend/v54.0-b33d96911 and update the enterprise multi-tenant README checklist for §0.4.5.

Notes

• Perfetto submodule change is Gracker/perfetto@b33d96911a28cc12036427f004e62e92865b4448 on fork/feature/enterprise-multi-tenant-tp-proxy.
• §0.4.3 remains unchecked because the 100MB / 500MB / 1GB trace matrix has not been completed in this slice.

Validation

• cd backend && npm test -- --runInBand src/routes/__tests__/traceProcessorProxyRoutes.test.ts
• cd backend && npm test -- --runInBand src/routes/__tests__/enterpriseTraceMetadataRoutes.test.ts src/routes/__tests__/traceProcessorProxyRoutes.test.ts
• cd backend && npm run typecheck
• cd backend && npm run test:core
• cd perfetto/ui && npm run build
• cd perfetto/ui && node build.js --no-build --run-unittests --test-filter "BackendUploader request context|SessionManager pending backend trace storage|HttpRpcEngine target selection"
• git diff --check HEAD^ HEAD
• npm run verify:pr
• Dev smoke: opened http://localhost:10000, verified Perfetto UI loaded; only expected local RPC probe / external manifest console noise appeared.

[Gracker]

已通过 commit 67856ec (merge) + 023a84a (frontend rebuild) 合入 main，关闭此 PR。