Add mock LED device type for testing without hardware

Virtual device with configurable LED count, RGB/RGBW mode, and simulated
send latency. Includes full provider/client implementation, API schema
support, and frontend add/settings modal integration.

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

server/src/wled_controller/api/routes/devices.py

@@ -44,6 +44,8 @@ def _device_to_response(device) -> DeviceResponse:
         enabled=device.enabled,
         baud_rate=device.baud_rate,
         auto_shutdown=device.auto_shutdown,
+        send_latency_ms=device.send_latency_ms,
+        rgbw=device.rgbw,
         capabilities=sorted(get_device_capabilities(device.device_type)),
         created_at=device.created_at,
         updated_at=device.updated_at,
@@ -116,6 +118,8 @@ async def create_device(
             device_type=device_type,
             baud_rate=device_data.baud_rate,
             auto_shutdown=auto_shutdown,
+            send_latency_ms=device_data.send_latency_ms or 0,
+            rgbw=device_data.rgbw or False,
         )
 
         # Register in processor manager for health monitoring
@@ -242,6 +246,8 @@ async def update_device(
             led_count=update_data.led_count,
             baud_rate=update_data.baud_rate,
             auto_shutdown=update_data.auto_shutdown,
+            send_latency_ms=update_data.send_latency_ms,
+            rgbw=update_data.rgbw,
         )
 
         # Sync connection info in processor manager