perf: add scalability benchmarks

[ShashankShekhar31]

Summary

• Add k6 performance tests for authentication flows.
• Add health endpoint scalability testing.
• Add horizontal API instance testing.
• Add Bitcoin/Esplora RPC latency testing.
• Add PostgreSQL read/query benchmark coverage.
• Add Kafka → consumer inbox → Temporal event-processing benchmark.
• Add a dedicated performance identity setup script.
• Document local performance SLOs and benchmark coverage.

Validation

• git diff --check ✅
• pnpm run format:check ✅
• pnpm typecheck ✅
• pnpm test ✅

Benchmark Results

• Health scalability: 20 VUs, 0% HTTP failures, p95 2.85 ms.
• Auth login: 0% HTTP failures, p95 ~110 ms.
• Event pipeline: 40/40 processed, 0 retries, consumer p95 40 ms.
• Bitcoin RPC: covered through k6.
• PostgreSQL read/query-plan: covered through pgbench.
• Horizontal API testing: covered through k6.

Notes

Portfolio, asset-query, and transaction API load tests are pending until the corresponding read endpoints are available.