Add configurable baud rate for Adalight with dynamic FPS hint

Baud rate is now a first-class device field, passed through the full
stack: Device model → API schemas → routes → ProcessorManager →
AdalightClient. The frontend shows a baud rate dropdown (115200–2M)
for Adalight devices in both Add Device and Settings modals, with a
live "Max FPS ≈ N" hint computed from LED count and baud rate.

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

server/src/wled_controller/main.py

@@ -155,6 +155,7 @@ async def lifespan(app: FastAPI):
                 led_count=device.led_count,
                 calibration=device.calibration,
                 device_type=device.device_type,
+                baud_rate=device.baud_rate,
             )
             logger.info(f"Registered device: {device.name} ({device.id})")
         except Exception as e: