Fix mobile color picker popup clipping and locale update for tabs/sections

Color picker popover now uses fixed positioning on small screens to
escape the header toolbar overflow container. Section titles, sub-tab
labels, and filter placeholders use data-i18n attributes so they update
automatically on language change. Display picker title switches to
"Select a Device" for engine-owned display lists.

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

server/src/wled_controller/static/css/layout.css

@@ -278,6 +278,7 @@ h2 {
 }
 .color-picker-popover.anchor-right { right: 0; }
 .color-picker-popover.anchor-left  { left: 0; }
+.color-picker-popover.cp-fixed { z-index: 1000; }
 @keyframes color-picker-pop-in {
     from { opacity: 0; transform: translateY(-4px) scale(0.95); }
     to   { opacity: 1; transform: translateY(0) scale(1); }