Add support for forwarding headers options

src/FrameProcessor/Configuration/ForwardedHeadersOptions.cs

@@ -0,0 +1,16 @@
+namespace FrameProcessor.Configuration;
+
+/// <summary>
+/// Bound from the <c>ForwardedHeaders</c> section of <c>appsettings.json</c>.
+/// Controls which upstream proxies are trusted to set <c>X-Forwarded-*</c> headers.
+/// Empty lists trust any upstream — only safe when the listening port is not
+/// publicly reachable (e.g. Docker network).
+/// </summary>
+public sealed class ForwardedHeadersOptions
+{
+    public const string SectionName = "ForwardedHeaders";
+
+    public List<string> KnownNetworks { get; set; } = new();
+
+    public List<string> KnownProxies { get; set; } = new();
+}