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/static/style.css

@@ -1160,6 +1160,13 @@ input:-webkit-autofill:focus {
     font-size: 0.85rem;
 }
 
+.fps-hint {
+    display: block;
+    margin-top: 4px;
+    font-size: 0.82rem;
+    color: var(--info-color, #2196F3);
+}
+
 .slider-row {
     display: flex;
     align-items: center;