please provide the full complete improved code with the best style all modals and scripts everything please :

<?php
declare(strict_types=1);
session_start();

// Set Content-Type to HTML initially
header('Content-Type: text/html; charset=utf-8');

// Enhanced Content Security Policy
header("Content-Security-Policy: default-src 'self'; script-src 'self' https://cdn.jsdelivr.net https://cdnjs.cloudflare.com 'unsafe-inline'; style-src 'self' https://cdn.jsdelivr.net https://cdnjs.cloudflare.com 'unsafe-inline'; img-src 'self' https://source.unsplash.com data:; font-src 'self' https://cdnjs.cloudflare.com; connect-src 'self'; object-src 'none'; frame-ancestors 'self'; base-uri 'self';");

// Strict Transport Security
header("Strict-Transport-Security: max-age=31536000; includeSubDomains; preload");

// Set other security headers
header('X-Content-Type-Options: nosniff');
header('X-Frame-Options: DENY');
header('Referrer-Policy: no-referrer-when-downgrade');

// CSRF Token Generation
if (empty($_SESSION['csrf_token'])) {
    $_SESSION['csrf_token'] = bin2hex(random_bytes(32));
}

// Handle AJAX POST Request for Contact Form Submission
if ($_SERVER['REQUEST_METHOD'] === 'POST' && isset($_POST['action']) && $_POST['action'] === 'submit_contact') {
    header('Content-Type: application/json; charset=utf-8');

    // Initialize Response Array
    $response = ['success' => false, 'message' => 'Invalid request.'];

    // CSRF Token Validation
    if (!isset($_POST['csrf_token']) || !hash_equals($_SESSION['csrf_token'], $_POST['csrf_token'])) {
        $response['message'] = 'Invalid CSRF token.';
        echo json_encode($response);
        exit;
    }

    // Input Validation and Sanitization
    $name = trim(filter_input(INPUT_POST, 'name', FILTER_SANITIZE_FULL_SPECIAL_CHARS));
    $email = filter_input(INPUT_POST, 'email', FILTER_VALIDATE_EMAIL);
    $message = trim(filter_input(INPUT_POST, 'message', FILTER_SANITIZE_FULL_SPECIAL_CHARS));

    if (!$name || !$email || !$message) {
        $response['message'] = 'All fields are required and must be valid.';
        echo json_encode($response);
        exit;
    }

    // Additional Validation for Name and Message Length
    if (strlen($name) > 100) {
        $response['message'] = 'Name is too long.';
        echo json_encode($response);
        exit;
    }

    if (strlen($message) > 1000) {
        $response['message'] = 'Message is too long.';
        echo json_encode($response);
        exit;
    }

    // Function to send email securely
    function send_contact_email(string $name, string $email, string $message): bool {
        $to = 'info@skypulse.uk'; // Replace with your email
        $subject = 'New Contact Message from ' . $name;
        $body = "Name: {$name}\nEmail: {$email}\n\nMessage:\n{$message}";

        // Sanitize email headers to prevent header injection
        $clean_email = filter_var($email, FILTER_SANITIZE_EMAIL);
        $clean_email = filter_var($clean_email, FILTER_VALIDATE_EMAIL);

        if (!$clean_email) {
            return false;
        }

        $headers = "From: {$clean_email}\r\n";
        $headers .= "Reply-To: {$clean_email}\r\n";
        $headers .= "Content-Type: text/plain; charset=UTF-8\r\n";

        // Attempt to send the email
        return mail($to, $subject, $body, $headers);
    }

    // Send Email
    if (send_contact_email($name, $email, $message)) {
        $response['success'] = true;
        $response['message'] = 'Your message has been sent successfully!';
    } else {
        $response['message'] = 'Failed to send your message. Please try again later.';
    }

    echo json_encode($response);
    exit;
}

// Page Content Variables
$title = "SkyPulse IT Services";
$description = "Leading the way in IT solutions with innovation and excellence. Offering remote support, hardware repair, system architecture, and more.";
$aboutContent = "At SkyPulse.uk, we transform the way businesses operate by providing cutting-edge IT solutions focused on customer satisfaction and tailored to meet your unique needs.";
$services = [
    ["icon" => "headset", "title" => "Remote Customer Support", "description" => "Efficient remote support via ticketing systems and professional emails for seamless customer assistance."],
    ["icon" => "tools", "title" => "Computer Hardware Repair & Upgrade", "description" => "Expert computer hardware repair and upgrades for optimal performance."],
    ["icon" => "diagnoses", "title" => "BSOD Diagnosis & Repair", "description" => "Specialized BSOD diagnosis and swift repair solutions for system stability."],
    ["icon" => "network-wired", "title" => "Windows System Architect", "description" => "Strategic architect optimizing Windows environments with Active Directory, RDP, and VPN."],
    ["icon" => "project-diagram", "title" => "Network Infrastructure Specialist", "description" => "Experienced in TCP/IP, LAN/WLAN, Wi-Fi, VPN, DHCP, Port Forwarding, Switching, and Routing."],
    ["icon" => "clone", "title" => "Digital Duplication", "description" => "Cloning and Resilient Backup & Recovery Mastery."]
];
$contactDescription = "Whether you have questions or need assistance, feel free to contact us. We're here to support your IT journey.";
?>
<!DOCTYPE html>
<html lang="en" data-theme="dark">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title><?= htmlspecialchars($title, ENT_QUOTES, 'UTF-8'); ?></title>
    <meta name="description" content="<?= htmlspecialchars($description, ENT_QUOTES, 'UTF-8'); ?>">
    <meta name="keywords" content="IT Services, Remote Support, Hardware Repair, System Architecture, Network Specialist, Digital Duplication">
    <meta name="author" content="SkyPulse.uk">
    <meta name="csrf-token" content="<?= $_SESSION['csrf_token']; ?>">

    <!-- Bootstrap 5.3.2 CSS -->
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/css/bootstrap.min.css" rel="stylesheet" integrity="sha384-lsAhncIoLzp0OnEbxJmXUcNexhSthTzduUO6P2B2hciiT9xOvn/TBnphF8WZYdMm" crossorigin="anonymous">

    <!-- Font Awesome 6.4.0 -->
    <link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.4.0/css/all.min.css" rel="stylesheet" integrity="sha512-pkg2X0g+z5+OZ+5vVwRTx5p9s5hSL2Q3Zy4wVfhKYx5J5MRUfFKCLtXzqH4v+Kp5Jw667jPHiQmf/gYip1R3Qg==" crossorigin="anonymous" referrerpolicy="no-referrer" />

    <!-- Google Fonts -->
    <link href="https://fonts.googleapis.com/css2?family=Montserrat:wght@600&family=Roboto:wght@400;700&display=swap" rel="stylesheet">

    <!-- Custom Styles -->
    <style>
        /* [Same CSS as before, no significant changes needed] */
        /* ... (keep the style definitions as they are, or make improvements if desired) */
    </style>
</head>
<body>
    <!-- Navigation Bar -->
    <nav class="navbar navbar-expand-lg navbar-dark fixed-top shadow-lg">
        <div class="container">
            <a class="navbar-brand" href="#"><?= htmlspecialchars($title, ENT_QUOTES, 'UTF-8'); ?></a>
            <button class="navbar-toggler" type="button" data-bs-toggle="collapse" data-bs-target="#navbarNav" 
                    aria-controls="navbarNav" aria-expanded="false" aria-label="Toggle navigation">
                <span class="navbar-toggler-icon"></span>
            </button>
            <div class="collapse navbar-collapse justify-content-end" id="navbarNav">
                <ul class="navbar-nav me-3">
                    <li class="nav-item"><a class="nav-link" href="#" data-bs-toggle="modal" data-bs-target="#aboutModal">About</a></li>
                    <li class="nav-item"><a class="nav-link" href="#" data-bs-toggle="modal" data-bs-target="#servicesModal">Services</a></li>
                    <li class="nav-item"><a class="nav-link" href="#" data-bs-toggle="modal" data-bs-target="#contactModal">Contact</a></li>
                    <li class="nav-item"><a class="nav-link" href="#" data-bs-toggle="modal" data-bs-target="#privacyModal">Privacy Policy</a></li>
                </ul>
                <!-- Theme Toggle Switch -->
                <div class="form-check form-switch text-nowrap">
                    <input class="form-check-input" type="checkbox" id="themeSwitch" aria-label="Toggle Light/Dark Mode">
                    <label class="form-check-label" for="themeSwitch">
                        <i class="fas fa-sun"></i>
                        <i class="fas fa-moon"></i>
                    </label>
                </div>
            </div>
        </div>
    </nav>

    <!-- Jumbotron Section with Parallax -->
    <section class="jumbotron text-center">
        <div class="container">
            <h1 class="display-4"><?= htmlspecialchars($title, ENT_QUOTES, 'UTF-8'); ?></h1>
            <p class="lead"><?= htmlspecialchars($description, ENT_QUOTES, 'UTF-8'); ?></p>
            <a href="#" class="btn btn-primary mt-3" data-bs-toggle="modal" data-bs-target="#contactModal">Get Started</a>
        </div>
    </section>

    <!-- Include the Modals and Rest of the Content -->
    <!-- [Same as before, unless you wish to make specific improvements to the content or structure] -->
    <!-- ... (include About Modal, Services Modal, Contact Modal, Privacy Modal, Services Section, Benefits Section, Footer) -->

    <!-- Footer -->
    <footer>
        <div class="container">
            <div class="mb-3 footer-links">
                <a href="#" data-bs-toggle="modal" data-bs-target="#aboutModal">About</a> |
                <a href="#" data-bs-toggle="modal" data-bs-target="#servicesModal">Services</a> |
                <a href="#" data-bs-toggle="modal" data-bs-target="#contactModal">Contact</a> |
                <a href="#" data-bs-toggle="modal" data-bs-target="#privacyModal">Privacy Policy</a>
            </div>
            <p>&copy; <?= date("Y"); ?> SkyPulse.uk. All Rights Reserved.</p>
            <!-- Google AdSense Placeholder -->
            <div class="adsense-placeholder">
                <span>Ad Space - Replace with Google AdSense Code</span>
            </div>
        </div>
    </footer>

    <!-- Bootstrap 5.3.2 JS Bundle (includes Popper.js) -->
    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.2/dist/js/bootstrap.bundle.min.js" integrity="sha384-spjEkyVJ+JHlXVI4RMT7HQkT+c7pI39t2r8Jq2kFAf23lafYgyDtX+zsy4OJKdF+" crossorigin="anonymous"></script>

    <!-- Custom JavaScript -->
    <script>
        document.addEventListener('DOMContentLoaded', () => {
            // Theme Toggle Functionality
            const themeSwitch = document.getElementById('themeSwitch');
            const currentTheme = localStorage.getItem('theme') || 'dark';

            // Apply the saved theme or default
            document.documentElement.setAttribute('data-theme', currentTheme);

            // Set the toggle state based on the current theme
            themeSwitch.checked = currentTheme === 'light';

            // Event listener for theme toggle
            themeSwitch.addEventListener('change', () => {
                const theme = themeSwitch.checked ? 'light' : 'dark';
                document.documentElement.setAttribute('data-theme', theme);
                localStorage.setItem('theme', theme);
            });

            // Form Submission with Fetch API
            const contactForm = document.getElementById('contactForm');
            const formFeedback = document.getElementById('formFeedback');

            contactForm.addEventListener('submit', async (event) => {
                event.preventDefault();
                event.stopPropagation();

                if (!contactForm.checkValidity()) {
                    contactForm.classList.add('was-validated');
                    return;
                }

                // Prepare Form Data
                const formData = new FormData(contactForm);

                try {
                    const response = await fetch(location.pathname, { // Submitting to the same page
                        method: 'POST',
                        body: formData,
                        headers: {
                            'Accept': 'application/json'
                        }
                    });

                    const result = await response.json();

                    if (response.ok && result.success) {
                        formFeedback.innerHTML = '<div class="alert alert-success">Your message has been sent successfully!</div>';
                        contactForm.reset();
                        contactForm.classList.remove('was-validated');
                    } else {
                        formFeedback.innerHTML = `<div class="alert alert-danger">${result.message || 'There was an error sending your message. Please try again later.'}</div>`;
                    }
                } catch (error) {
                    formFeedback.innerHTML = '<div class="alert alert-danger">There was an error processing your request. Please try again later.</div>';
                    console.error('Error:', error);
                }
            });

            // Remove feedback on input change
            ['input', 'textarea'].forEach(tag => {
                contactForm.querySelectorAll(tag).forEach(element => {
                    element.addEventListener('input', () => {
                        formFeedback.innerHTML = '';
                    });
                }); 
            });
        });
    </script>
</body>
</html>