Add Art-Net / sACN (E1.31) DMX device support

Full-stack implementation of DMX output for stage lighting and LED controllers:
- DMXClient with Art-Net and sACN packet builders, multi-universe splitting
- DMXDeviceProvider with manual_led_count capability and URL parsing
- Device store, API schemas, routes wired with dmx_protocol/start_universe/start_channel
- Frontend: add/settings modals with DMX fields, IconSelect protocol picker
- Fix add device modal dirty check on type change (re-snapshot after switch)
- i18n keys for DMX in en/ru/zh locales

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

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

@@ -54,6 +54,9 @@ def _device_to_response(device) -> DeviceResponse:
         zone_mode=device.zone_mode,
         capabilities=sorted(get_device_capabilities(device.device_type)),
         tags=getattr(device, 'tags', []),
+        dmx_protocol=getattr(device, 'dmx_protocol', 'artnet'),
+        dmx_start_universe=getattr(device, 'dmx_start_universe', 0),
+        dmx_start_channel=getattr(device, 'dmx_start_channel', 1),
         created_at=device.created_at,
         updated_at=device.updated_at,
     )
@@ -129,6 +132,9 @@ async def create_device(
             rgbw=device_data.rgbw or False,
             zone_mode=device_data.zone_mode or "combined",
             tags=device_data.tags,
+            dmx_protocol=device_data.dmx_protocol or "artnet",
+            dmx_start_universe=device_data.dmx_start_universe or 0,
+            dmx_start_channel=device_data.dmx_start_channel or 1,
         )
 
         # WS devices: auto-set URL to ws://{device_id}
@@ -313,6 +319,9 @@ async def update_device(
             rgbw=update_data.rgbw,
             zone_mode=update_data.zone_mode,
             tags=update_data.tags,
+            dmx_protocol=update_data.dmx_protocol,
+            dmx_start_universe=update_data.dmx_start_universe,
+            dmx_start_channel=update_data.dmx_start_channel,
         )
 
         # Sync connection info in processor manager