Read constraints from the published URDF rather than hard code them.

Also make the webui more responsive for small screens.

webui/backend/main.py

@@ -54,6 +54,7 @@ async def lifespan(app: FastAPI):
     node = start_ros()
     node.on_joint_states_callbacks.append(manager.broadcast_from_thread)
     node.on_ultrasonic_callbacks.append(manager.broadcast_from_thread)
+    node.on_joint_limits_callbacks.append(manager.broadcast_from_thread)
     yield
     stop_ros()
 
@@ -65,6 +66,10 @@ app = FastAPI(lifespan=lifespan)
 async def websocket_endpoint(ws: WebSocket):
     await manager.connect(ws)
     node = get_node()
+    # Send cached joint limits immediately so the client doesn't wait for the next publish
+    cached_limits = node.get_joint_limits()
+    if cached_limits:
+        await ws.send_json({'type': 'joint_limits', 'limits': cached_limits})
     try:
         while True:
             data = await ws.receive_json()