feat: add default map setting feature

Add ability to set a specific map as the default that opens on load:

- Add 'Open default map' option to onload behavior dropdown
- Implement saveAsDefaultMap() to store map as default in IndexedDB
- Implement clearDefaultMap() to remove default map setting
- Modify checkLoadParameters() to load default map when configured
- Add UI buttons in Save dialog for setting/clearing default map
- Update version to 1.108.12 and hash in index.html

Users can now:
1. Open any map they want as default
2. Go to Options > Onload behavior > Select "Open default map"
3. Save > Click "Set as default" button
4. The map will now open automatically every time

This sets the foundation for the planned time-based worldbuilding
and lore database features by ensuring users always start with
their primary world map.

main.js

@@ -291,6 +291,22 @@ async function checkLoadParameters() {
     return;
   }
 
+  // check if there is a default map saved to indexedDB
+  if (byId("onloadBehavior").value === "default") {
+    try {
+      const blob = await ldb.get("defaultMap");
+      if (blob) {
+        WARN && console.warn("Loading default map");
+        uploadMap(blob);
+        return;
+      } else {
+        WARN && console.warn("No default map set, generating random map");
+      }
+    } catch (error) {
+      ERROR && console.error(error);
+    }
+  }
+
   // check if there is a map saved to indexedDB
   if (byId("onloadBehavior").value === "lastSaved") {
     try {