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/locales/zh.json

@@ -38,6 +38,7 @@
   "displays.none": "没有可用的显示器",
   "displays.failed": "加载显示器失败",
   "displays.picker.title": "选择显示器",
+  "displays.picker.title.device": "选择设备",
   "displays.picker.select": "选择显示器...",
   "displays.picker.click_to_select": "点击选择此显示器",
   "displays.picker.adb_connect": "连接 ADB 设备",