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

routes/auth.py

@@ -0,0 +1,62 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# Copyright Hersel Giannella
+
+"""
+Authentication routes for login/logout
+"""
+
+from flask import Blueprint, render_template, request, redirect, url_for, flash
+from flask_login import login_user, logout_user, current_user
+from models import User, db
+from datetime import datetime
+
+route_auth = Blueprint('auth', __name__, url_prefix='/auth')
+
+
+@route_auth.route('/login', methods=['GET', 'POST'])
+def login():
+    """Login page"""
+    # Se l'utente è già autenticato, reindirizza alla dashboard
+    if current_user.is_authenticated:
+        return redirect(url_for('admin.dashboard'))
+
+    if request.method == 'POST':
+        username = request.form.get('username')
+        password = request.form.get('password')
+        remember = request.form.get('remember', False)
+
+        if not username or not password:
+            flash('Per favore inserisci username e password.', 'danger')
+            return render_template('auth/login.html')
+
+        user = User.query.filter_by(username=username).first()
+
+        if user and user.check_password(password):
+            if not user.is_active:
+                flash('Il tuo account è stato disabilitato.', 'danger')
+                return render_template('auth/login.html')
+
+            # Aggiorna last_login
+            user.last_login = datetime.utcnow()
+            db.session.commit()
+
+            login_user(user, remember=remember)
+            flash(f'Benvenuto {user.username}!', 'success')
+
+            # Redirect alla pagina richiesta o alla dashboard
+            next_page = request.args.get('next')
+            return redirect(next_page) if next_page else redirect(url_for('admin.dashboard'))
+        else:
+            flash('Username o password non corretti.', 'danger')
+
+    return render_template('auth/login.html')
+
+
+@route_auth.route('/logout')
+def logout():
+    """Logout user"""
+    logout_user()
+    flash('Logout effettuato con successo.', 'info')
+    return redirect(url_for('route_home.home'))