feat: expand secret redaction patterns
Added 14 new redaction patterns, all with distinctive prefixes
that have near-zero false positive risk:
Prefix patterns:
- AWS Access Key ID (AKIA...)
- Stripe keys (sk_live_, sk_test_, rk_live_)
- SendGrid (SG....)
- HuggingFace (hf_...)
- Replicate (r8_...)
- npm tokens (npm_...)
- PyPI tokens (pypi-...)
- DigitalOcean PATs (dop_v1_, doo_v1_)
- AgentMail (am_...)
Structural patterns:
- Private key blocks (-----BEGIN...PRIVATE KEY-----)
- Database connection string passwords (postgres://user:PASS@host)
aaf8f2d2d2