refactor(gateway): harden proxy client ip resolution

src/gateway/http-endpoint-helpers.ts

@@ -12,6 +12,7 @@ export async function handleGatewayPostJsonEndpoint(
     auth: ResolvedGatewayAuth;
     maxBodyBytes: number;
     trustedProxies?: string[];
+    allowRealIpFallback?: boolean;
     rateLimiter?: AuthRateLimiter;
   },
 ): Promise<false | { body: unknown } | undefined> {
@@ -30,6 +31,7 @@ export async function handleGatewayPostJsonEndpoint(
     res,
     auth: opts.auth,
     trustedProxies: opts.trustedProxies,
+    allowRealIpFallback: opts.allowRealIpFallback,
     rateLimiter: opts.rateLimiter,
   });
   if (!authorized) {