Add Logout Endpoint and Dashboard Logout Button

[alvarotech]

Description

The application currently has authentication functionality with login and register features, but lacks a proper logout endpoint on the backend and a logout button in the dashboard UI. While the frontend has logout logic implemented in the auth context, we need:

1. A backend logout endpoint following the project's hexagonal architecture
2. A logout button in the dashboard header (top-right position) for easy access

Current State

• ✅ Frontend logout logic exists in useAuthContext.tsx
• ✅ Frontend auth service has logout function calling /api/v1/auth/logout
• ❌ Backend /api/v1/auth/logout endpoint is missing
• ❌ Dashboard lacks visible logout button

Requirements

Backend

• Add POST /api/v1/auth/logout endpoint in /backend/src/infrastructure/web/routers/users.py
• Follow hexagonal architecture patterns (use case → domain → infrastructure)
• Handle token invalidation/blacklisting if needed
• Return appropriate HTTP status codes

Frontend

• Add logout button to dashboard header (/frontend/src/pages/home.page.tsx)
• Position button in top-right corner of the header
• Use existing useAuthContext hook for logout functionality
• Ensure logout redirects to login page
• Follow project's feature-based architecture and UI conventions

Acceptance Criteria

• Backend endpoint POST /api/v1/auth/logout is implemented
• Endpoint follows hexagonal architecture patterns
• Endpoint returns 200 status on successful logout
• Frontend dashboard has logout button in header top-right position
• Logout button uses existing auth context logout function
• Clicking logout button clears user session and redirects to /login
• Button follows project's UI design patterns (Radix UI/TailwindCSS)
• All existing authentication tests continue to pass
• New functionality includes appropriate error handling

Technical Notes

Backend Implementation

• Location: /backend/src/infrastructure/web/routers/users.py
• Should be added near existing auth endpoints (register, login)
• Consider if token blacklisting is needed for security
• Follow existing dependency injection patterns

Frontend Implementation

• Location: /frontend/src/pages/home.page.tsx header section
• Use existing useAuthContext hook: const { logout } = useAuthContext()
• Style with TailwindCSS to match existing UI components
• Consider adding user email/avatar next to logout button

Priority

Medium - Important for user experience and security best practices