Expand hardcoded secret detection using open-source references

[sarahxsanders]

Context

From Vincent's review on PR #14 — the current hardcoded secret rules cover AWS, GitHub PAT, and Stripe live keys. There are many more secret formats worth detecting.

Reference projects to pull patterns from

• TruffleHog: https://github.com/trufflesecurity/trufflehog/tree/main/pkg/detectors
• detect-secrets (Yelp): https://github.com/Yelp/detect-secrets/tree/master/detect_secrets/plugins
• Secret Parker (Praetorian): https://github.com/praetorian-inc/titus/tree/main/pkg/rule/rules

High-value candidates to add next

• Slack tokens (xoxb-, xoxp-, xoxs-)
• Twilio keys (SK + 32 hex)
• SendGrid keys (SG.)
• Database connection strings (postgres://, mongodb://, mysql://)
• Generic JWT detection
• OpenAI / Anthropic API keys
• Datadog / New Relic API keys

Origin

PR #14 review comment by @gewenyu99