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-calculation.php

@@ -0,0 +1,96 @@
+<?php
+
+declare(strict_types=1);
+
+echo "=== Syndrome Calculation Test ===\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: Create a simple RS code manually
+// For RS(7, 4): 4 data codewords, 3 EC codewords
+$data = [1, 2, 3, 4];
+$ecCodewords = 3;
+
+// Generator polynomial for degree 3: g(x) = (x-α^0)(x-α^1)(x-α^2)
+// = x^3 + (α^0+α^1+α^2)x^2 + (α^0*α^1 + α^0*α^2 + α^1*α^2)x + (α^0*α^1*α^2)
+// In GF(256): α^0=1, α^1=2, α^2=4
+// g(x) = x^3 + 7x^2 + 14x + 8
+
+$generator = [1, 7, 14, 8]; // Monic polynomial
+
+// Manual encoding
+$msg = array_merge($data, array_fill(0, $ecCodewords, 0));
+
+for ($i = 0; $i < count($data); $i++) {
+    $lead = $msg[$i];
+    if ($lead !== 0) {
+        $msg[$i] = 0;
+        for ($j = 1; $j < count($generator); $j++) {
+            $msg[$i + $j] ^= gfMult($gfExp, $gfLog, $generator[$j], $lead);
+        }
+    }
+}
+
+$ec = array_slice($msg, count($data));
+echo "Data: " . implode(', ', $data) . "\n";
+echo "EC: " . implode(', ', $ec) . "\n";
+echo "Full: " . implode(', ', array_merge($data, $ec)) . "\n\n";
+
+// Calculate syndromes
+echo "Calculating syndromes:\n";
+$full = array_merge($data, $ec);
+$syndromes = [];
+
+for ($i = 0; $i < $ecCodewords; $i++) {
+    $alphaPower = $gfExp[$i]; // α^i
+    $syndrome = 0;
+    $power = 1; // (α^i)^0 = 1
+    
+    for ($j = 0; $j < count($full); $j++) {
+        $syndrome ^= gfMult($gfExp, $gfLog, $full[$j], $power);
+        $power = gfMult($gfExp, $gfLog, $power, $alphaPower);
+    }
+    
+    $syndromes[$i] = $syndrome;
+    echo "  S[{$i}] = {$syndrome}\n";
+}
+
+$allZero = true;
+foreach ($syndromes as $s) {
+    if ($s !== 0) {
+        $allZero = false;
+        break;
+    }
+}
+
+if ($allZero) {
+    echo "\n✅ All syndromes are zero - RS encoding is CORRECT!\n";
+    echo "\nThis means our algorithm is correct.\n";
+    echo "The problem might be with the generator polynomial format.\n";
+} else {
+    echo "\n❌ Syndromes are not all zero - RS encoding is WRONG!\n";
+}
+
+