Fix DDP streaming and capture thread safety

- Fix WLED DDP config: use lor=0 (live overrides effects), remove
  live flag (read-only, causes issues on 0.15.x), disable PUSH flag
  which broke rendering on WLED 0.15.x
- Use dedicated single-thread executor for capture engine calls to
  fix thread-local state issues with BetterCam/MSS/DXcam
- Sync processor state on stream/template change even when stopped,
  preventing stale engine references on next start
- Add diagnostic logging for frame sends and DDP packets

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/api/routes.py

@@ -427,14 +427,29 @@ async def update_device(
             picture_stream_id=update_data.picture_stream_id,
         )
 
-        # Hot-swap: If stream/template changed and device was processing, restart it
-        if (stream_changed or template_changed) and was_processing:
-            logger.info(f"Hot-swapping stream/template for device {device_id}")
-            try:
-                # Stop current processing
-                await manager.stop_processing(device_id)
-
-                # Update processor with new settings
+        # Sync processor state when stream/template changed
+        if stream_changed or template_changed:
+            if was_processing:
+                # Hot-swap: restart with new settings
+                logger.info(f"Hot-swapping stream/template for device {device_id}")
+                try:
+                    await manager.stop_processing(device_id)
+                    manager.remove_device(device_id)
+                    manager.add_device(
+                        device_id=device.id,
+                        device_url=device.url,
+                        led_count=device.led_count,
+                        settings=device.settings,
+                        calibration=device.calibration,
+                        capture_template_id=device.capture_template_id,
+                        picture_stream_id=device.picture_stream_id,
+                    )
+                    await manager.start_processing(device_id)
+                    logger.info(f"Successfully hot-swapped stream/template for device {device_id}")
+                except Exception as e:
+                    logger.error(f"Error during template hot-swap: {e}")
+            else:
+                # Not processing — update processor state so next start uses new values
                 manager.remove_device(device_id)
                 manager.add_device(
                     device_id=device.id,
@@ -446,14 +461,6 @@ async def update_device(
                     picture_stream_id=device.picture_stream_id,
                 )
 
-                # Restart processing
-                await manager.start_processing(device_id)
-                logger.info(f"Successfully hot-swapped stream/template for device {device_id}")
-
-            except Exception as e:
-                logger.error(f"Error during template hot-swap: {e}")
-                # Device is stopped but updated - user can manually restart
-
         return DeviceResponse(
             id=device.id,
             name=device.name,