Add group leader functionality and update group member management

- Create GroupLeader model and migration
- Alter GroupLeader member field to include related_name
- Implement is_leader and is_owner methods in Group model
- Update GroupDetailView to pass leader and owner status to template
- Refactor group buttons and members display into separate templates
- Add view and URL for setting group leaders
- Update permissions for adding/removing members and clearing blacklist
- Bump version to 0.1.1 in uv.lock

uv.lock

@@ -423,7 +423,7 @@ wheels = [
 
 [[package]]
 name = "musik"
-version = "0.1.0"
+version = "0.1.1"
 source = { virtual = "." }
 dependencies = [
     { name = "celery" },