fix: exempt admins from default user group limits

crates/aether-data/migrations/sqlite/20260509120000_add_user_groups.sql

@@ -97,4 +97,5 @@ VALUES (
 INSERT OR IGNORE INTO user_group_members (group_id, user_id, created_at)
 SELECT '00000000-0000-0000-0000-000000000001', id, CAST(strftime('%s', 'now') AS INTEGER)
 FROM users
-WHERE is_deleted = 0;
+WHERE is_deleted = 0
+  AND LOWER(role) <> 'admin';

crates/aether-data/migrations/sqlite/20260511120000_exclude_admins_from_default_user_group.sql

@@ -0,0 +1,14 @@
+DELETE FROM user_group_members
+WHERE user_id IN (
+    SELECT id
+    FROM users
+    WHERE LOWER(role) = 'admin'
+)
+  AND (
+    group_id = '00000000-0000-0000-0000-000000000001'
+    OR group_id IN (
+      SELECT TRIM(value, '"')
+      FROM system_configs
+      WHERE key = 'default_user_group_id'
+    )
+  );