Much simpler undo/redo handling, bugs fixed and less code.

src/components/HeaderControls.vue

@@ -95,6 +95,10 @@ function toggleVisibility() {
 // Settings dialog integration
 const settingsDialog = ref(null)
 function openSettings() {
+  // Capture baseline before opening settings
+  try {
+    calendarStore.$history?._baselineIfNeeded?.(true)
+  } catch {}
   settingsDialog.value?.open()
 }