perf: visibility-gate dashboard render loop

Co-authored-by: PR0M3TH3AN <[email protected]>

dashboard/index.html

@@ -814,11 +814,17 @@
       // Periodic TTL refresh
       // -----------------------------------------------------------------------
       refreshIntervalId = setInterval(() => {
-        if (isAlive()) {
+        if (isAlive() && !document.hidden) {
           renderLocks();
         }
       }, 30_000);
 
+      document.addEventListener('visibilitychange', () => {
+        if (!document.hidden && isAlive()) {
+          renderLocks();
+        }
+      });
+
       // -----------------------------------------------------------------------
       // Event handlers
       // -----------------------------------------------------------------------