fix: COD-29 harden downloads and extract auth policy

src/web/network-auth-policy.ts

@@ -0,0 +1,21 @@
+import { isIP } from 'node:net';
+
+const EXPLICIT_TRUE_VALUES = new Set(['1', 'true', 'yes', 'on']);
+
+export function isExplicitlyEnabled(value: string | undefined): boolean {
+  return value !== undefined && EXPLICIT_TRUE_VALUES.has(value.trim().toLowerCase());
+}
+
+export function isLoopbackBindHost(host: string): boolean {
+  const normalized = host
+    .trim()
+    .toLowerCase()
+    .replace(/^\[(.*)\]$/, '$1');
+  if (normalized === 'localhost' || normalized === '::1' || normalized === '0:0:0:0:0:0:0:1') {
+    return true;
+  }
+  if (isIP(normalized) === 4 && normalized.startsWith('127.')) {
+    return true;
+  }
+  return normalized.startsWith('::ffff:127.');
+}