- Add helmet for HTTP security headers (CSP, HSTS, X-Frame-Options, etc.) - Add @nestjs/throttler for rate limiting (100 req/60s per IP) - Add shared secret validation on Signal webhook endpoint - Remove JWT token from localStorage, use Auth0 SDK memory cache with async getAccessTokenSilently() in API interceptor - Restrict hard delete (?hard=true) to ADMINISTRATOR role in service layer - Replace exposed Anthropic API key with placeholder in .env Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>