Add command palette entity selector for all editor dropdowns

Replace plain <select> dropdowns with a searchable command palette modal
for 16 entity selectors across 6 editors (targets, streams, CSS sources,
value sources, audio sources, pattern templates). Unified EntityPalette
singleton + EntitySelect wrapper in core/entity-palette.js.

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

server/src/wled_controller/static/js/features/pattern-templates.js

@@ -21,6 +21,9 @@ import { showToast, showConfirm } from '../core/ui.js';
 import { Modal } from '../core/modal.js';
 import { getPictureSourceIcon, ICON_PATTERN_TEMPLATE, ICON_CLONE, ICON_EDIT } from '../core/icons.js';
 import { wrapCard } from '../core/card-colors.js';
+import { EntitySelect } from '../core/entity-palette.js';
+
+let _patternBgEntitySelect = null;
 
 class PatternTemplateModal extends Modal {
     constructor() {
@@ -88,6 +91,20 @@ export async function showPatternTemplateEditor(templateId = null, cloneData = n
             bgSelect.appendChild(opt);
         });
 
+        // Entity palette for background source
+        if (_patternBgEntitySelect) _patternBgEntitySelect.destroy();
+        if (sources.length > 0) {
+            _patternBgEntitySelect = new EntitySelect({
+                target: bgSelect,
+                getItems: () => sources.map(s => ({
+                    value: s.id,
+                    label: s.name,
+                    icon: getPictureSourceIcon(s.stream_type),
+                })),
+                placeholder: t('palette.search'),
+            });
+        }
+
         setPatternEditorBgImage(null);
         setPatternEditorSelectedIdx(-1);
         setPatternCanvasDragMode(null);