feat(gateway): add trusted-proxy auth mode (#15940)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: 279d4b304f83186fda44dfe63a729406a835dafa
Co-authored-by: nickytonline <833231+nickytonline@users.noreply.github.com>
Co-authored-by: steipete <58493+steipete@users.noreply.github.com>
Reviewed-by: @steipete

src/cli/gateway-cli/run.ts

@@ -247,7 +247,7 @@ async function runGatewayCommand(opts: GatewayRunOpts) {
     defaultRuntime.exit(1);
     return;
   }
-  if (bind !== "loopback" && !hasSharedSecret) {
+  if (bind !== "loopback" && !hasSharedSecret && resolvedAuthMode !== "trusted-proxy") {
     defaultRuntime.error(
       [
         `Refusing to bind gateway to ${bind} without auth.`,