Add EntitySelect/IconSelect UI improvements across modals

- Portal IconSelect popups to document.body with position:fixed to prevent
  clipping by modal overflow-y:auto
- Replace custom scene selectors in automation editor with EntitySelect
  command-palette pickers (main scene + fallback scene)
- Add IconSelect grid for automation deactivation mode (none/revert/fallback)
- Add IconSelect grid for automation condition type and match type
- Replace mapped zone source dropdowns with EntitySelect pickers
- Replace scene target selector with EntityPalette.pick() pattern
- Remove effect palette preview bar from CSS editor
- Remove sensitivity badge from audio color strip source cards
- Clean up unused scene-selector CSS and scene-target-add-row CSS
- Add locale keys for all new UI elements across en/ru/zh

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

server/src/wled_controller/static/css/modal.css

@@ -760,14 +760,6 @@
 
 /* ── Gradient editor ────────────────────────────────────────────── */
 
-.effect-palette-preview {
-    width: 100%;
-    height: 20px;
-    border-radius: 6px;
-    margin-top: 6px;
-    border: 1px solid var(--border-color);
-}
-
 .gradient-editor {
     position: relative;
     width: 100%;