Add three layers of secret leak prevention:
1. .gitleaks.toml — config extending the default ruleset (~150 rules for
AWS, GCP, Stripe, OpenAI, private keys, JWTs, etc.) with allowlists
tuned to suppress false positives from test fixtures and docs.
2. .husky/pre-commit — enhanced with gitleaks protect --staged (graceful
skip if not installed), sensitive file type blocking (.pem, .key, .enc,
id_rsa, etc.), and broadened fallback patterns covering AWS, OpenAI,
GCP, and private key headers alongside existing Stripe checks.
3. .github/workflows/build-and-test.yml — new secret-scan CI job using
gitleaks-action that runs in parallel with build on every push/PR,
serving as the last gate if someone bypasses local hooks.