feat: Navigation hinzugefügt und URL-Struktur in .htaccess optimiert

app/templates/header.php

@@ -26,8 +26,36 @@
 <header>
     <h1>Netzwerk-Dokumentation</h1>
 
-    <!-- TODO: Navigation einfügen -->
-    <!-- Beispiel: Links zu Dashboard, Gerätetypen, Geräte, Racks, Floors, Connections -->
+    <?php
+    $currentPath = parse_url($_SERVER['REQUEST_URI'], PHP_URL_PATH);
+
+    $navItems = [
+        '/' => 'Dashboard',
+        '/device-types' => 'Gerätetypen',
+        '/devices' => 'Geräte',
+        '/racks' => 'Racks',
+        '/floors' => 'Grundrisse',
+        '/connections' => 'Verbindungen',
+    ];
+    ?>
+
+    <nav class="main-nav">
+        <ul>
+            <?php foreach ($navItems as $url => $label): ?>
+                <?php
+                    $active = ($currentPath === $url || str_starts_with($currentPath, $url . '/'))
+                        ? 'active'
+                        : '';
+                ?>
+                <li class="<?= $active ?>">
+                    <a href="<?= htmlspecialchars($url) ?>">
+                        <?= htmlspecialchars($label) ?>
+                    </a>
+                </li>
+            <?php endforeach; ?>
+        </ul>
+    </nav>
+
 </header>
 
 <main>