Add iOS node push-token registration foundation

src/gateway/handlers/config.ts

@@ -158,6 +158,11 @@ const PATCHABLE_KEYS: Record<string, (config: Config, value: unknown) => boolean
     config.server.nodes.location.enabled = value;
     return true;
   },
+  'server.nodes.push.enabled': (config, value) => {
+    if (typeof value !== 'boolean') {return false;}
+    config.server.nodes.push.enabled = value;
+    return true;
+  },
 };
 
 export function createConfigHandlers(deps: ConfigHandlerDeps) {