Add authentication system and admin dashboard

Security Features:
- Added User model with bcrypt password hashing
- Implemented Flask-Login for session management
- Protected all API write operations with @login_required decorator
- Added authentication routes (login/logout)

Admin Dashboard:
- Created comprehensive admin dashboard with statistics
- Profile management interface
- Skills management (add/edit/delete)
- Projects management with full CRUD operations
- Social links management
- Modern responsive UI with Bootstrap 5

New Files:
- models.py: Added User model with bcrypt
- routes/auth.py: Login/logout functionality
- routes/admin.py: Complete admin dashboard with CRUD operations
- templates/auth/login.html: Login page
- templates/admin/base.html: Admin base template
- templates/admin/dashboard.html: Main dashboard
- templates/admin/profile.html: Profile editor
- templates/admin/skills.html: Skills manager
- templates/admin/projects.html: Projects list
- templates/admin/project_form.html: Project editor
- templates/admin/social_links.html: Social links manager

Modified Files:
- app.py: Integrated Flask-Login and bcrypt, registered new blueprints
- requirements.txt: Added Flask-Login, Flask-Bcrypt, bcrypt
- init_db.py: Creates default admin user (admin/admin123)
- routes/api.py: Protected all write operations with authentication

Default Credentials:
- Username: admin
- Password: admin123
- ⚠️ MUST be changed after first login!

Benefits:
- Secure API access with session-based authentication
- User-friendly admin interface for content management
- No need to edit code or database directly
- Bcrypt password hashing for security
- Protected against unauthorized access

requirements.txt

@@ -7,6 +7,11 @@ itsdangerous==2.2.0
 MarkupSafe==3.0.2
 blinker==1.9.0
 
+# Authentication
+Flask-Login==0.6.3
+Flask-Bcrypt==1.0.1
+bcrypt==4.2.1
+
 # Database - Flask-SQLAlchemy and MariaDB/MySQL driver
 Flask-SQLAlchemy==3.1.1
 SQLAlchemy==2.0.36