🛡️ Sentinel: [HIGH] Fix hardcoded JWT secret fallback in AuthService

[Pmaster-dev]

🛡️ Sentinel PR: Fix hardcoded JWT secret fallback

🚨 Severity: HIGH
💡 Vulnerability: server/services/AuthService.ts fell back to a hardcoded default string ("negrarosa-inclusive-security-framework-secret") when process.env.JWT_SECRET was undefined.
🎯 Impact: Attackers aware of the default secret could forge JWT tokens to impersonate users and bypass authentication.
🔧 Fix: Updated AuthService constructor to throw a critical error if JWT_SECRET is missing in production (NODE_ENV === "production"), and updated the dev fallback secret to explicitly indicate development-only usage.
✅ Verification: Tested constructor instantiation under development and production environments via tsx node script to verify runtime guard behavior.

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PR created automatically by Jules for task 1298358912787598792 started by @Pmaster-dev

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