chore: import upstream snapshot with attribution

cli-tool/components/commands/security/add-authentication-system.md

@@ -0,0 +1,33 @@
+---
+allowed-tools: Read, Write, Edit, Bash
+argument-hint: [auth-method] | --oauth | --jwt | --mfa | --passwordless
+description: Implement secure user authentication system with chosen method and security best practices
+---
+
+# Add Authentication System
+
+Implement secure user authentication system: **$ARGUMENTS**
+
+## Current Application State
+
+- Framework detection: @package.json or @requirements.txt or @Cargo.toml
+- Existing auth: !`grep -r "auth\|login\|jwt\|session" src/ --include="*.js" --include="*.py" --include="*.rs" | wc -l`
+- Security config: @.env* (check for auth-related variables)
+- Database setup: Check for user models or auth tables
+
+## Task
+
+Implement comprehensive authentication system with security best practices:
+
+**Authentication Methods**: Choose from username/password, OAuth 2.0, JWT, SAML, MFA, or passwordless based on $ARGUMENTS
+
+**Implementation Areas**:
+1. **User Management** - Registration, profiles, password policies, account verification
+2. **Authentication Flow** - Login/logout, session management, token handling, middleware
+3. **Authorization System** - RBAC, permissions, route protection, API security
+4. **Security Hardening** - Password hashing, rate limiting, CSRF protection, secure cookies
+5. **Integration** - Frontend components, API endpoints, database models, middleware
+
+**Security Standards**: Implement OWASP authentication guidelines, secure session management, and proper error handling.
+
+**Output**: Production-ready authentication system with comprehensive security controls and user-friendly interface.