fix: engine REST API - handle GET/DELETE requests immediately, use user-provided node IDs

- Use lws_http_get_uri_and_method() for proper HTTP method detection
  (GET, POST, PUT, DELETE all supported)
- Handle GET/DELETE in LWS_CALLBACK_HTTP without waiting for body
- Support user-provided node IDs via config.id field
- Fixes all REST API endpoints hanging on GET requests

libs/dmf-engine/src/graph.cpp

@@ -7,7 +7,12 @@
 namespace dmf_engine {
 
 NodeId Graph::add_node(const std::string& type, const nlohmann::json& config) {
-    auto id = type + "_" + std::to_string(next_node_num_++);
+    std::string id;
+    if (config.contains("id") && config["id"].is_string()) {
+        id = config["id"].get<std::string>();
+    } else {
+        id = type + "_" + std::to_string(next_node_num_++);
+    }
     GraphNode node;
     node.id = id;
     node.type = type;