Style the pre-install initiating screen

Replace the unstyled “script is not installed” flash with a centered UNA mark and a pulsing “Initiating Installation” line. Hold 1.4s so the pulse is visible, then redirect to install/.

index.php

@@ -15,11 +15,78 @@ if (!file_exists("./inc/header.inc.php")) {
     header("Cache-Control: no-cache, must-revalidate");
     header("Pragma: no-cache");
 
-    echo "It seems to be script is <b>not</b> installed.<br />\n";
-    if ( file_exists( "install/index.php" ) ) {
-        echo "Please, wait. Redirecting you to installation form...<br />\n";
-        echo "<script language=\"javascript\">location.href = 'install/index.php';</script>\n";
-    }
+    $bHasInstaller = file_exists("install/index.php");
+    $sTitle = $bHasInstaller ? 'Initiating Installation' : 'Installation files are missing';
+    header('Content-Type: text/html; charset=utf-8');
+    ?>
+<!DOCTYPE html>
+<html lang="en">
+<head>
+    <meta charset="utf-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <title><?php echo htmlspecialchars($sTitle, ENT_QUOTES, 'UTF-8'); ?></title>
+<?php if ($bHasInstaller): ?>
+    <meta http-equiv="refresh" content="2;url=install/index.php" />
+<?php endif; ?>
+    <style>
+        :root {
+            --bx-flash-bg: #f4f5f7;
+            --bx-flash-text: #111827;
+            --bx-flash-muted: #6b7280;
+            --bx-flash-font: ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
+        }
+        html, body {
+            margin: 0;
+            height: 100%;
+        }
+        body {
+            min-height: 100vh;
+            display: flex;
+            align-items: center;
+            justify-content: center;
+            background: var(--bx-flash-bg);
+            font-family: var(--bx-flash-font);
+            color: var(--bx-flash-text);
+            -webkit-font-smoothing: antialiased;
+        }
+        .bx-install-flash {
+            text-align: center;
+            padding: 24px;
+        }
+        .bx-install-flash img {
+            display: block;
+            width: 64px;
+            height: 64px;
+            margin: 0 auto 20px;
+            border-radius: 16px;
+        }
+        .bx-install-flash p {
+            margin: 0;
+            font-size: 16px;
+            font-weight: 550;
+            letter-spacing: -0.01em;
+            color: var(--bx-flash-muted);
+        }
+        .bx-install-flash-pulse {
+            animation: bx-install-flash-pulse 1.4s ease-in-out infinite;
+        }
+        @keyframes bx-install-flash-pulse {
+            0%, 100% { opacity: 0.35; }
+            50% { opacity: 1; }
+        }
+    </style>
+</head>
+<body>
+    <div class="bx-install-flash">
+        <img src="install/img/logo.svg" alt="UNA" />
+        <p class="bx-install-flash-pulse"><?php echo htmlspecialchars($sTitle, ENT_QUOTES, 'UTF-8'); ?></p>
+    </div>
+<?php if ($bHasInstaller): ?>
+    <script>setTimeout(function () { location.href = 'install/index.php'; }, 1400);</script>
+<?php endif; ?>
+</body>
+</html>
+    <?php
     exit;
 }