fix(security): harden security across auth, API, frontend, and infra

[thlaure]

Summary

• Auth: Replace assert() with AccessDeniedException in all state processors/providers; prevent user enumeration on register (generic 201 response); enforce PasswordStrength(MEDIUM) on registration
• SSRF: Add SsrfSafeUrl custom validator, applied to feed URL input
• XSS: Sanitize article HTML with DOMPurify before rendering
• Infra: Add Content-Security-Policy header in Caddyfile; clear hardcoded secrets from .env/.env.dev; prevent raw exception messages leaking from feed crawl errors
• CI: Add composer audit, npm audit, TruffleHog secret scanning; enforce typecheck and lint (remove || true)
• Behat: Fix api_platform.yaml formats accidentally scoped under when@prod; update test passwords to pass strength check

Test plan

• All Behat API tests pass (57/57)
• make quality passes (lint, PHPStan, Rector)
• PHPUnit unit tests pass
• Frontend builds without error (npm run build)
• Register endpoint returns generic 201 for both new and existing emails

🤖 Generated with Claude Code

[gitguardian]

⚠️ GitGuardian has uncovered 1 secret following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

🔎 Detected hardcoded secret in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
28737789	Triggered	Company Email Password	f2313b3	features/api/register.feature	View secret

🛠 Guidelines to remediate hardcoded secrets

1. Understand the implications of revoking this secret by investigating where it is used in your code.
2. Replace and store your secret safely. Learn here the best practices.
3. Revoke and rotate this secret.
4. If possible, rewrite git history. Rewriting git history is not a trivial act. You might completely break other contributing developers' workflow and you risk accidentally deleting legitimate data.

To avoid such incidents in the future consider

• following these best practices for managing and storing secrets including API keys and other credentials
• install secret detection on pre-commit to catch secret before it leaves your machine and ease remediation.

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