Add performance benchmark and soak validation

[XploitGost]

Summary

• add safe synthetic benchmarks for all five bounded pipeline stages
• add configurable full-pipeline soak test with CPU/RSS and Ops health metrics
• generate centrally redacted JSON and Markdown reports
• document methodology, reference results, tuning, and limitations
• add CI-safe structural benchmark tests

Validation

• Backend: 309/309 passed
• Frontend: 43/43 passed
• Frontend build: passed
• 10-second soak: 2000 processed, 0 dropped, 0 failed, all stages bounded
• PyInstaller packaged backend smoke: passed
• Production npm audit: 0 vulnerabilities

No live capture, external networking, admin privileges, or new operational/security features are introduced by the benchmark suite.