refactor(deployment): Remove WireGuard VPN dependency and restore public service access

Remove WireGuard integration from production deployment to simplify infrastructure:
- Remove docker-compose-direct-access.yml (VPN-bound services)
- Remove VPN-only middlewares from Grafana, Prometheus, Portainer
- Remove WireGuard middleware definitions from Traefik
- Remove WireGuard IPs (10.8.0.0/24) from Traefik forwarded headers

All monitoring services now publicly accessible via subdomains:
- grafana.michaelschiemer.de (with Grafana native auth)
- prometheus.michaelschiemer.de (with Basic Auth)
- portainer.michaelschiemer.de (with Portainer native auth)

All services use Let's Encrypt SSL certificates via Traefik.

tests/debug/test-qrcode-png-generation.php

@@ -0,0 +1,71 @@
+<?php
+
+declare(strict_types=1);
+
+require_once __DIR__ . '/../../vendor/autoload.php';
+
+use App\Framework\QrCode\QrCodeGenerator;
+use App\Framework\QrCode\ValueObjects\ErrorCorrectionLevel;
+use App\Framework\QrCode\ValueObjects\QrCodeConfig;
+use App\Framework\QrCode\ValueObjects\QrCodeVersion;
+use App\Framework\QrCode\ValueObjects\EncodingMode;
+
+echo "=== PNG QR Code Generation for Testing ===\n\n";
+
+$testData = 'HELLO WORLD';
+$config = new QrCodeConfig(
+    version: QrCodeVersion::fromNumber(1),
+    errorCorrectionLevel: ErrorCorrectionLevel::M,
+    encodingMode: EncodingMode::BYTE
+);
+
+$matrix = QrCodeGenerator::generate($testData, $config);
+$size = $matrix->getSize();
+
+// Generate high-quality PNG
+$moduleSize = 20;
+$quietZone = 4;
+$canvasSize = ($size + 2 * $quietZone) * $moduleSize;
+
+echo "Matrix: {$size}x{$size}\n";
+echo "Module size: {$moduleSize}px\n";
+echo "Quiet zone: {$quietZone} modules\n";
+echo "Canvas: {$canvasSize}x{$canvasSize}px\n\n";
+
+$image = imagecreatetruecolor($canvasSize, $canvasSize);
+$white = imagecolorallocate($image, 255, 255, 255);
+$black = imagecolorallocate($image, 0, 0, 0);
+
+imagefill($image, 0, 0, $white);
+
+$offset = $quietZone * $moduleSize;
+
+for ($row = 0; $row < $size; $row++) {
+    for ($col = 0; $col < $size; $col++) {
+        if ($matrix->getModuleAt($row, $col)->isDark()) {
+            $x = $offset + ($col * $moduleSize);
+            $y = $offset + ($row * $moduleSize);
+            
+            imagefilledrectangle(
+                $image,
+                $x,
+                $y,
+                $x + $moduleSize - 1,
+                $y + $moduleSize - 1,
+                $black
+            );
+        }
+    }
+}
+
+$outputDir = __DIR__ . '/test-qrcodes';
+$filepath = $outputDir . '/scannable-hello-world.png';
+imagepng($image, $filepath, 0);
+
+echo "✅ PNG generated: {$filepath}\n";
+echo "   Size: {$canvasSize}x{$canvasSize}px\n";
+echo "   File size: " . filesize($filepath) . " bytes\n\n";
+
+echo "This PNG should be scannable.\n";
+echo "Please test it with your smartphone scanner.\n";
+