refactor: clean ONLYOFFICE integration - remove workarounds, follow standard pattern

static/app.js

@@ -693,14 +693,4 @@ function formatDate(d) {
 }
 
 // Initial load
-loadDashboard();
-
-// Restore active page after an ONLYOFFICE editor close triggered a page reload
-(function() {
-  var returnPage = sessionStorage.getItem('returnPage');
-  if (returnPage) {
-    sessionStorage.removeItem('returnPage');
-    var link = document.querySelector('[data-page="' + returnPage + '"]');
-    if (link) link.click();
-  }
-})();
+loadDashboard();