🛡️ Sentinel: [CRITICAL] Fix Hardcoded Authentication Secrets and 2FA Bypasses

[secrooq]

🚨 Severity: CRITICAL
💡 Vulnerability: The application relied on hardcoded fallbacks for AUTH_SECRET in NextAuth and src/middleware.ts, and utilized a static backdoor string (stealth_dev_bypass_root_2026) for bypassing 2FA during admin recovery.
🎯 Impact: If these files were leaked, an attacker could easily spoof valid administrative sessions using the known NextAuth encryption keys, or completely bypass the Two-Factor Authentication requirement for administrative users using the static backdoor string.
🔧 Fix: Removed the static string fallbacks from g.process.env edge initialization in both src/auth.ts and src/middleware.ts. Replaced the static string fallback for NextAuth secret initialization with strict environment variable retrieval. Replaced the static 2FA backdoor expected secret with strict environment variable enforcement (process.env.ADMIN_BYPASS_SECRET).
✅ Verification: Ran unit tests (pnpm test) and production end-to-end tests (npx playwright test), both of which passed with the updated strict environment variables injected via test runtime configurations. Added the findings to .jules/sentinel.md journal.

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PR created automatically by Jules for task 12492422081940115033 started by @secrooq

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