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-polynomial-division-fix.php

@@ -0,0 +1,68 @@
+<?php
+
+declare(strict_types=1);
+
+require_once __DIR__ . '/../../vendor/autoload.php';
+
+use App\Framework\QrCode\ErrorCorrection\ReedSolomonEncoder;
+
+echo "=== Polynomial Division Fix Test ===\n\n";
+
+// Test with simple data
+$data = [1, 2, 3];
+$ecCodewords = 3;
+
+$rs = new ReedSolomonEncoder();
+$reflection = new ReflectionClass($rs);
+
+// Get generator polynomial
+$getGeneratorMethod = $reflection->getMethod('getGeneratorPolynomial');
+$getGeneratorMethod->setAccessible(true);
+$generator = $getGeneratorMethod->invoke($rs, $ecCodewords);
+
+echo "Generator polynomial: " . implode(', ', $generator) . "\n";
+echo "Note: First coefficient is 0, which is unusual.\n\n";
+
+// The issue might be that we're using the generator polynomial incorrectly
+// In standard Reed-Solomon, the generator polynomial is monic (leading coefficient = 1)
+// But our stored polynomials start with 0
+
+// Let's check if we should skip the first coefficient
+if ($generator[0] === 0) {
+    echo "Generator polynomial starts with 0 - this might be the issue.\n";
+    echo "In standard RS, generator should be monic (leading coefficient = 1).\n\n";
+    
+    // Try without the first coefficient
+    $generatorWithoutZero = array_slice($generator, 1);
+    echo "Generator without leading 0: " . implode(', ', $generatorWithoutZero) . "\n";
+    echo "This would be a monic polynomial of degree " . (count($generatorWithoutZero) - 1) . "\n\n";
+}
+
+// Test the actual encoding
+$ec = $rs->encode($data, $ecCodewords);
+echo "EC codewords: " . implode(', ', $ec) . "\n\n";
+
+// Now let's verify with our decoder
+require_once __DIR__ . '/test-reed-solomon-decoder.php';
+
+$fullCodeword = array_merge($data, $ec);
+$decoder = new SimpleRSDecoder();
+$syndromes = $decoder->calculateSyndromes($fullCodeword, $ecCodewords);
+
+echo "Syndromes: " . implode(', ', $syndromes) . "\n";
+$allZero = true;
+foreach ($syndromes as $s) {
+    if ($s !== 0) {
+        $allZero = false;
+        break;
+    }
+}
+
+if ($allZero) {
+    echo "✅ All syndromes are zero - codeword is valid!\n";
+} else {
+    echo "❌ Syndromes are not all zero - codeword is invalid!\n";
+    echo "\nThe problem is in the polynomial division algorithm.\n";
+}
+
+