feat: add trufflehog secret scanning (hooks + CI)

[rohan-naik]

Adds filesystem secret scanning with trufflehog, wired identically into local git hooks and CI so the two cannot drift apart. Mirrors contentstack/rte-micro-frontend#66.

What's included

• scripts/trufflehog-scan.sh — the shared scan script. Scans the current filesystem (tracked + untracked, non-gitignored files mirrored into a temp tree), never git history. Mirroring means gitignored local files such as an .npmrc auth token can't fail the hook. It fails closed: an empty scan set, a missing trufflehog, or a broken scan all block rather than pass.
• .husky/pre-commit and .husky/pre-push — run that script locally. husky added as a devDependency with "prepare": "husky".
• .github/workflows/secret-scan.yml — runs the same script on PRs and pushes to main. Scans the whole checked-out tree rather than the PR diff: a secret already on the branch is a leak regardless of which commit introduced it.
• scripts/trufflehog-exclude.txt — excluded paths (node_modules/, dist/, build/, coverage/, package-lock.json, .npmrc).

Difference from the reference PR: the CI push trigger targets main, this repo's default branch, rather than master.

Testing

Verified locally with trufflehog 3.96.0:

Case	Result
Clean tree	no secrets found, exit 0
Planted realistic AWS key	potential secrets found. Aborted., exit 1
Real git commit with that file staged	Blocked by husky, no commit created
Real git push	pre-push hook ran and passed

Note for reviewers

Developers need trufflehog installed locally (brew install trufflehog) or the hooks will block with install instructions. package-lock.json also carries some npm-generated churn beyond the husky entry, from regenerating against the current tree.

🤖 Generated with Claude Code

[snyk-io]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues
✅	Code Security	0	0	0	0	0 issues

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[github-actions]

🔒 Security Scan Results

ℹ️ Note: Only vulnerabilities with available fixes (upgrades or patches) are counted toward thresholds.

Check Type	Count (with fixes)	Without fixes	Threshold	Result
🔴 Critical Severity	0	0	10	✅ Passed
🟠 High Severity	0	0	25	✅ Passed
🟡 Medium Severity	0	0	0	✅ Passed
🔵 Low Severity	0	0	0	✅ Passed

⏱️ SLA Breach Summary

✅ No SLA breaches detected. All vulnerabilities are within acceptable time thresholds.

Severity	Breaches (with fixes)	Breaches (no fixes)	SLA Threshold (with/no fixes)	Status
🔴 Critical	0	0	15 / 30 days	✅ Passed
🟠 High	0	0	30 / 120 days	✅ Passed
🟡 Medium	0	0	90 / 365 days	✅ Passed
🔵 Low	0	0	180 / 365 days	✅ Passed

✅ BUILD PASSED - All security checks passed