fix: toolbar buttons clickable, add node delete

Fixes:
- SVG mousedown handler now ignores clicks outside SVG (toolbar works)
- Right-click node -> Destroy Node to delete virtual devices
- POST /api/destroy-node {node_id} endpoint (uses pw-cli destroy)

Node context menu shows node name and destroy button.

src/web_server.cpp

@@ -450,6 +450,37 @@ void WebServer::setupRoutes() {
     m_http.Options("/api/create-loopback", cors_handler);
     m_http.Options("/api/unload-module", cors_handler);
     m_http.Options("/api/load-module", cors_handler);
+    m_http.Options("/api/destroy-node", cors_handler);
+
+    // Destroy node: POST /api/destroy-node {"node_id":N}
+    m_http.Post("/api/destroy-node", [this](const httplib::Request &req, httplib::Response &res) {
+        uint32_t node_id = 0;
+        if (sscanf(req.body.c_str(), "{\"node_id\":%u}", &node_id) == 1) {
+            // Find the module that owns this node and unload it
+            // First try to destroy via registry (works for pw-cli created nodes)
+            auto snap = m_engine.snapshot();
+            bool found = false;
+            for (auto &n : snap.nodes) {
+                if (n.id == node_id) {
+                    found = true;
+                    break;
+                }
+            }
+            if (found) {
+                // Use pw-cli to destroy
+                std::string cmd = "pw-cli destroy " + std::to_string(node_id) + " 2>/dev/null";
+                int ret = system(cmd.c_str());
+                (void)ret;
+                sleep(1);
+                broadcastGraph();
+            }
+            res.set_content(found ? "{\"ok\":true}" : "{\"ok\":false,\"error\":\"node not found\"}", "application/json");
+        } else {
+            res.status = 400;
+            res.set_content("{\"error\":\"invalid json\"}", "application/json");
+        }
+        res.set_header("Access-Control-Allow-Origin", "*");
+    });
 
     // Helper: extract a string value from simple JSON
     auto extractStr = [](const std::string &body, const std::string &key) -> std::string {