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-syndrome-codeword-order.php

@@ -0,0 +1,123 @@
+<?php
+
+declare(strict_types=1);
+
+require_once __DIR__ . '/../../vendor/autoload.php';
+
+echo "=== Syndrome Calculation with Codeword Order ===\n\n";
+
+// Reference data and EC codewords
+$data = [64, 180, 132, 84, 196, 196, 242, 5, 116, 245, 174, 59, 64, 109, 236, 233];
+$ec = [0, 245, 228, 127, 21, 207, 194, 102, 66, 52];
+
+echo "Data codewords: " . implode(', ', $data) . "\n";
+echo "EC codewords: " . implode(', ', $ec) . "\n\n";
+
+// Initialize GF(256)
+$gfLog = array_fill(0, 256, 0);
+$gfExp = array_fill(0, 512, 0);
+
+$x = 1;
+for ($i = 0; $i < 255; $i++) {
+    $gfExp[$i] = $x;
+    $gfLog[$x] = $i;
+    $x <<= 1;
+    if ($x & 0x100) {
+        $x ^= 0x11d;
+    }
+}
+
+for ($i = 255; $i < 512; $i++) {
+    $gfExp[$i] = $gfExp[$i - 255];
+}
+
+function gfMult(array $gfExp, array $gfLog, int $a, int $b): int
+{
+    if ($a === 0 || $b === 0) return 0;
+    return $gfExp[$gfLog[$a] + $gfLog[$b]];
+}
+
+// Test 1: Forward order (data first, then EC)
+$codeword1 = array_merge($data, $ec);
+echo "Test 1: Forward order (data + EC)\n";
+$syndromes1 = [];
+for ($i = 0; $i < 10; $i++) {
+    $alphaPower = $gfExp[$i];
+    $syndrome = 0;
+    $power = 1;
+    for ($j = 0; $j < count($codeword1); $j++) {
+        $syndrome ^= gfMult($gfExp, $gfLog, $codeword1[$j], $power);
+        $power = gfMult($gfExp, $gfLog, $power, $alphaPower);
+    }
+    $syndromes1[$i] = $syndrome;
+}
+echo "Syndromes: " . implode(', ', $syndromes1) . "\n";
+$allZero1 = array_sum($syndromes1) === 0;
+echo ($allZero1 ? "✅" : "❌") . " All zero\n\n";
+
+// Test 2: Reversed order (EC first, then data)
+$codeword2 = array_merge($ec, $data);
+echo "Test 2: Reversed order (EC + data)\n";
+$syndromes2 = [];
+for ($i = 0; $i < 10; $i++) {
+    $alphaPower = $gfExp[$i];
+    $syndrome = 0;
+    $power = 1;
+    for ($j = 0; $j < count($codeword2); $j++) {
+        $syndrome ^= gfMult($gfExp, $gfLog, $codeword2[$j], $power);
+        $power = gfMult($gfExp, $gfLog, $power, $alphaPower);
+    }
+    $syndromes2[$i] = $syndrome;
+}
+echo "Syndromes: " . implode(', ', $syndromes2) . "\n";
+$allZero2 = array_sum($syndromes2) === 0;
+echo ($allZero2 ? "✅" : "❌") . " All zero\n\n";
+
+// Test 3: Reversed codewords (each codeword reversed)
+$codeword3 = array_reverse(array_merge($data, $ec));
+echo "Test 3: Reversed codewords array\n";
+$syndromes3 = [];
+for ($i = 0; $i < 10; $i++) {
+    $alphaPower = $gfExp[$i];
+    $syndrome = 0;
+    $power = 1;
+    for ($j = 0; $j < count($codeword3); $j++) {
+        $syndrome ^= gfMult($gfExp, $gfLog, $codeword3[$j], $power);
+        $power = gfMult($gfExp, $gfLog, $power, $alphaPower);
+    }
+    $syndromes3[$i] = $syndrome;
+}
+echo "Syndromes: " . implode(', ', $syndromes3) . "\n";
+$allZero3 = array_sum($syndromes3) === 0;
+echo ($allZero3 ? "✅" : "❌") . " All zero\n\n";
+
+// Test 4: Polynomial representation: c[0] is highest power
+// c(x) = c[0]*x^(n-1) + c[1]*x^(n-2) + ... + c[n-1]*x^0
+// Evaluate at α^i: c(α^i) = sum(c[j] * (α^i)^(n-1-j))
+$codeword4 = array_merge($data, $ec);
+$n = count($codeword4);
+echo "Test 4: MSB-first polynomial representation\n";
+$syndromes4 = [];
+for ($i = 0; $i < 10; $i++) {
+    $alphaPower = $gfExp[$i];
+    $syndrome = 0;
+    // Start with (α^i)^(n-1)
+    $power = $gfExp[($i * ($n - 1)) % 255];
+    for ($j = 0; $j < $n; $j++) {
+        $syndrome ^= gfMult($gfExp, $gfLog, $codeword4[$j], $power);
+        // Next: divide by α^i
+        $power = gfMult($gfExp, $gfLog, $power, $gfExp[255 - $i]);
+    }
+    $syndromes4[$i] = $syndrome;
+}
+echo "Syndromes: " . implode(', ', $syndromes4) . "\n";
+$allZero4 = array_sum($syndromes4) === 0;
+echo ($allZero4 ? "✅" : "❌") . " All zero\n\n";
+
+if ($allZero1 || $allZero2 || $allZero3 || $allZero4) {
+    echo "✅ Found correct order!\n";
+} else {
+    echo "❌ None of the orders work. The syndrome calculation might be fundamentally wrong.\n";
+}
+
+