Add privacy flag to upload — PII runs only when privacy=True (NDA mode)

Reduce default concurrent jobs to 5

perf: 8 workers, 10 concurrent uploads, Qdrant wait=False + batch 2000

production hardening: circuit breakers, graceful degradation, health checks, parallel uploads, HF Spaces deploy config

fix: 15 critical/high bugs across codebase

fix models.py: match Neon schema varchar sizes, add email unique constraint