fix: WebSocket control server - add HTTP mount for WS upgrade negotiation

LWS v4.x requires an HTTP mount with LWSMPRO_CALLBACK to properly
route WebSocket upgrade requests to the dmf-control protocol handler.
Without this, WS connections were rejected with 403 Forbidden.

libs/dmf-node/src/control_server.cpp

@@ -33,6 +33,12 @@ static int callback_ws(struct lws* wsi, enum lws_callback_reasons reason,
                        void* user, void* in, size_t len);
 
 static const struct lws_protocols protocols[] = {
+    {
+        "http-only",
+        callback_ws,
+        sizeof(ControlServerData*),
+        0,
+    },
     {
         "dmf-control",
         callback_ws,
@@ -119,6 +125,25 @@ static int callback_ws(struct lws* wsi, enum lws_callback_reasons reason,
     return 0;
 }
 
+static const struct lws_http_mount mount = {
+    .mount_next = nullptr,
+    .mountpoint = "/",
+    .origin = "",
+    .def = "",
+    .protocol = "dmf-control",
+    .cgienv = nullptr,
+    .extra_mimetypes = nullptr,
+    .interpret = nullptr,
+    .cgi_timeout = 0,
+    .cache_max_age = 0,
+    .auth_mask = 0,
+    .cache_reusable = 0,
+    .cache_revalidate = 0,
+    .cache_intermediaries = 0,
+    .origin_protocol = LWSMPRO_CALLBACK,
+    .mountpoint_len = 1,
+};
+
 ControlServer::ControlServer(uint16_t port, StatusCallback on_event)
     : impl_(std::make_unique<Impl>()) {
     impl_->port = port;
@@ -129,6 +154,7 @@ ControlServer::ControlServer(uint16_t port, StatusCallback on_event)
     std::memset(&info, 0, sizeof(info));
     info.port = port;
     info.protocols = protocols;
+    info.mounts = &mount;
     info.user = impl_->data.get();
     info.gid = -1;
     info.uid = -1;