fix: persist onloadBehavior setting for default map feature

The default map feature was not working on page refresh because the
onloadBehavior dropdown value was not being persisted or restored.

Changes:
- main.js: Restore onloadBehavior from localStorage on page load
- save.js: saveAsDefaultMap() now saves "default" to localStorage
- save.js: clearDefaultMap() now removes the localStorage setting
- index.html: Update version hashes to 1.108.13

Now when users click "Set as default", the setting persists across
page refreshes and their default map loads automatically.

main.js

@@ -291,6 +291,12 @@ async function checkLoadParameters() {
     return;
   }
 
+  // restore onloadBehavior from localStorage if saved
+  const storedBehavior = localStorage.getItem("onloadBehavior");
+  if (storedBehavior) {
+    byId("onloadBehavior").value = storedBehavior;
+  }
+
   // check if there is a default map saved to indexedDB
   if (byId("onloadBehavior").value === "default") {
     try {