Remove idle color feature, simplify power to turn-off only, fix settings serial port bug

- Remove static/idle color from entire stack (storage, API, processing, UI, CSS, locales)
- Simplify device power button to turn-off only (send black frame, no toggle)
- Send black frame on serial port close (AdalightClient.close)
- Fix settings modal serial port dropdown showing WLED devices due to stale deviceType

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

server/src/wled_controller/static/css/cards.css

@@ -423,39 +423,6 @@ section {
 }
 
 /* Static color picker — inline in card-subtitle */
-.static-color-control {
-    display: inline-flex;
-    align-items: center;
-    gap: 4px;
-}
-
-.static-color-picker {
-    width: 22px;
-    height: 18px;
-    padding: 0;
-    border: 1px solid var(--border-color);
-    border-radius: 3px;
-    cursor: pointer;
-    background: none;
-    vertical-align: middle;
-}
-
-.btn-clear-color {
-    background: none;
-    border: none;
-    color: #777;
-    font-size: 0.75rem;
-    cursor: pointer;
-    padding: 0 2px;
-    line-height: 1;
-    border-radius: 3px;
-    transition: color 0.2s;
-}
-
-.btn-clear-color:hover {
-    color: var(--danger-color);
-}
-
 .section-header {
     display: flex;
     align-items: center;