Fix target metrics showing --- by scoping querySelector to targets panel

The dashboard panel appears before the targets panel in the DOM and both
use data-target-id. document.querySelector was finding the dashboard
element (which has no data-tm children) instead of the target card.

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

server/src/wled_controller/static/js/features/targets.js

@@ -736,7 +736,9 @@ function _buildLedTimingHTML(state) {
 }
 
 function _patchTargetMetrics(target) {
-    const card = document.querySelector(`[data-target-id="${target.id}"]`);
+    const container = document.getElementById('targets-panel-content');
+    if (!container) return;
+    const card = container.querySelector(`[data-target-id="${target.id}"]`);
     if (!card) return;
     const state = target.state || {};
     const metrics = target.metrics || {};