feat: add node register endpoint and fabric create-target/connect APIs

- POST /api/graph/nodes/{id}/register: register manually-started node with control port
- POST /api/fabric/create-target: add_writer + poll for target_info
- POST /api/fabric/connect: auto-propagate target_info to initiator
- fabric-bridge: auto-fetch target_info from remote target via HTTP

libs/dmf-engine/src/api_server.cpp

@@ -321,6 +321,26 @@ static void handle_request(const std::string& method, const std::string& path,
             } else {
                 error_resp(500, "Failed to send command to node");
             }
+        } else if (path.find("/api/graph/nodes/") == 0 && path.find("/register") != std::string::npos && method == "POST") {
+            auto prefix = std::string("/api/graph/nodes/");
+            auto suffix_start = path.find("/register");
+            auto node_id = path.substr(prefix.length(), suffix_start - prefix.length());
+
+            if (!req_body.contains("port")) {
+                error_resp(400, "Missing port");
+                return;
+            }
+
+            auto control_port = static_cast<uint16_t>(req_body["port"].get<int>());
+            cc.register_node(node_id, control_port);
+
+            auto* node = graph.get_node_mut(node_id);
+            if (node) {
+                node->control_port = control_port;
+                node->state = NodeState::Running;
+            }
+
+            ok({{"node_id", node_id}, {"control_port", control_port}});
         } else if (path == "/api/fabric/create-target" && method == "POST") {
             if (!req_body.contains("node_id")) {
                 error_resp(400, "Missing node_id");