Fix section toggle firing on filter input drag

Changed header collapse from click to mousedown so dragging from the
filter input to outside no longer triggers a toggle.

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

server/src/wled_controller/static/js/core/card-sections.js

@@ -95,13 +95,13 @@ export class CardSection {
         const filterInput = document.querySelector(`[data-cs-filter="${this.sectionKey}"]`);
         if (!header || !content) return;
 
-        header.addEventListener('click', (e) => {
+        header.addEventListener('mousedown', (e) => {
             if (e.target.closest('.cs-filter')) return;
             this._toggleCollapse(header, content);
         });
 
         if (filterInput) {
-            filterInput.addEventListener('click', (e) => e.stopPropagation());
+            filterInput.addEventListener('mousedown', (e) => e.stopPropagation());
             let timer = null;
             filterInput.addEventListener('input', () => {
                 clearTimeout(timer);