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

base/static/css/main.css

@@ -122,3 +122,11 @@ footer {
     text-align: center;
     font-weight: 350;
 }
+
+td.c, th.c {
+    text-align: center;
+
+    input {
+        margin: 0;
+    }
+}