Add soft 404 error handling with errorController and template

Introduced `errorController` for handling unreachable pages with a soft 404 response. Added configurable error handling via `settings.development.ini` and implemented a new `error.tpl` template. Updated `dispatcher.php` to route non-existent pages to the error controller.

application/controller/errorController.php

@@ -0,0 +1,52 @@
+<?php
+namespace Nibiru;
+/**
+ * Class    errorController
+ * @project prod.maschinen-stockert.de
+ * @desc    Soft 404 error page handler for unreachable pages
+ * @author  Claude Code / Stephan Kasdorf
+ * @date    Dec 16 2024
+ * @package Nibiru
+ */
+
+use Nibiru\Adapter\Controller;
+use Nibiru\Module\{
+    Assetmanager\Plugins\Assetmanager,
+    Cms\Plugins\Cms,
+    Errorhandler\Plugins\Errorhandler
+};
+
+class errorController extends Controller
+{
+    private string $requestedUri = '';
+
+    public function __construct()
+    {
+        // Store the originally requested URI before routing to error
+        $this->requestedUri = $_SERVER['REQUEST_URI'] ?? '/';
+    }
+
+    public function pageAction()
+    {
+        // Set HTTP status code to 404 (while still rendering the page - soft 404)
+        http_response_code(404);
+
+        // Assign error-specific variables
+        View::assign([
+            'requestedUri' => htmlspecialchars($this->requestedUri, ENT_QUOTES, 'UTF-8'),
+            'errorCode' => '404',
+            'errorTitle' => 'Seite nicht gefunden',
+            'errorMessage' => 'Die angeforderte Seite konnte leider nicht gefunden werden.',
+            'errorSuggestion' => 'Die Seite wurde möglicherweise verschoben, gelöscht oder existiert nicht mehr.',
+            'metaRobots' => 'noindex, follow',
+            'homeUrl' => '/',
+            'contactUrl' => '/kontakt',
+            'machinesUrl' => '/maschinen'
+        ]);
+    }
+
+    public function navigationAction()
+    {
+        JsonNavigation::getInstance()->loadJsonNavigationArray();
+    }
+}