feat: added design for navbar and Background; edited DC-Handler; added roles for right calling; added check for highest role; added DC-Login page + Button

header.php

@@ -0,0 +1,17 @@
+<?php
+session_start();
+?>
+
+<nav>
+    <a href="index.php">Startseite</a>
+
+    <?php if (isset($_SESSION['user']) && $_SESSION['user']['hasRole']): ?>
+        <a href="admin.php">Admin-Menü</a>
+    <?php endif; ?>
+
+    <?php if (isset($_SESSION['user'])): ?>
+        <a href="logout.php">Logout</a>
+    <?php else: ?>
+        <a href="loginform.php">Login</a>
+    <?php endif; ?>
+</nav>