fix: Optimize multi-dongle inference for proper parallel processing

- Enable USB timeout (5000ms) for stable communication
- Fix send thread timeout from 0.01s to 1.0s for better blocking
- Update WebcamInferenceRunner to use async pattern (non-blocking)
- Add non-blocking put_input option to prevent frame drops
- Improve thread stopping mechanism with better cleanup

These changes follow Kneron official example pattern and should
enable proper parallel processing across multiple dongles.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

cluster4npu_ui/core/functions/Multidongle.py

@@ -289,9 +289,9 @@ class MultiDongle:
             sys.exit(1)
 
         # setting timeout of the usb communication with the device
-        # print('[Set Device Timeout]')
-        # kp.core.set_timeout(device_group=self.device_group, milliseconds=5000)
-        # print(' - Success')
+        print('[Set Device Timeout]')
+        kp.core.set_timeout(device_group=self.device_group, milliseconds=5000)
+        print(' - Success')
 
         # if self.upload_fw:
         try:
@@ -417,19 +417,19 @@ class MultiDongle:
 
             try:
                 # Get image and format from the input queue
-                # Blocks until an item is available or stop event is set/timeout occurs
+                # Block until an item is available
                 try:
-                    # Use get with timeout or check stop event in a loop
-                    # This pattern allows thread to check stop event while waiting on queue
-                    item = self._input_queue.get(block=True, timeout=0.1)
-                    # Check if this is our sentinel value
+                    item = self._input_queue.get(block=True, timeout=1.0)
+                    # Check if this is our sentinel value to stop
                     if item is None:
-                        continue
+                        break
                         
                     # Now safely unpack the tuple
                     image_data, image_format_enum = item
                 except queue.Empty:
-                    # If queue is empty after timeout, check stop event and continue loop
+                    # Check stop event and continue if timeout
+                    if self._stop_event.is_set():
+                        break
                     continue
 
                 # Configure and send the image
@@ -501,24 +501,26 @@ class MultiDongle:
         print("Stopping threads...")
         self._stop_event.set()
         
-        # Clear queues to unblock threads
-        while not self._input_queue.empty():
-            try:
-                self._input_queue.get_nowait()
-            except queue.Empty:
-                break
-        
-        # Signal send thread to wake up
-        self._input_queue.put(None)
+        # Signal send thread to stop by putting sentinel value
+        try:
+            self._input_queue.put(None, timeout=1.0)
+        except queue.Full:
+            # Clear queue if it's full and try again
+            while not self._input_queue.empty():
+                try:
+                    self._input_queue.get_nowait()
+                except queue.Empty:
+                    break
+            self._input_queue.put(None)
         
         # Join threads with timeout
         for thread, name in [(self._send_thread, "Send"), (self._receive_thread, "Receive")]:
             if thread and thread.is_alive():
-                thread.join(timeout=2.0)
+                thread.join(timeout=3.0)
                 if thread.is_alive():
                     print(f"Warning: {name} thread didn't stop cleanly")
         
-    def put_input(self, image: Union[str, np.ndarray], format: str, target_size: Tuple[int, int] = None):
+    def put_input(self, image: Union[str, np.ndarray], format: str, target_size: Tuple[int, int] = None, block: bool = True, timeout: float = None):
         """
         Put an image into the input queue with flexible preprocessing
         """
@@ -539,7 +541,13 @@ class MultiDongle:
         else:
             raise ValueError(f"Unsupported format: {format}")
 
-        self._input_queue.put((image_data, image_format_enum))
+        try:
+            self._input_queue.put((image_data, image_format_enum), block=block, timeout=timeout)
+        except queue.Full:
+            if not block:
+                print("Warning: Input queue is full, dropping frame")
+            else:
+                raise
 
     def get_output(self, timeout: float = None):
         """
@@ -687,12 +695,12 @@ class WebcamInferenceRunner:
                     self.display_fps_start_time = time.time()
                 self.display_frame_counter += 1
                 
-                # Preprocess and send frame
+                # Preprocess and send frame (non-blocking)
                 processed_frame = self.multidongle.preprocess_frame(frame, self.image_format)
-                self.multidongle.put_input(processed_frame, self.image_format)
+                self.multidongle.put_input(processed_frame, self.image_format, block=False)
                 
-                # Get inference result
-                prob, result = self.multidongle.get_latest_inference_result()
+                # Try to get inference result (non-blocking)
+                prob, result = self.multidongle.get_latest_inference_result(timeout=0.001)
                 if prob is not None:
                     # Track inference FPS
                     if self.inference_fps_start_time is None: