fix(models): correct UserSetting import namespace and add test coverage

.ai/rules/coverage.md

@@ -0,0 +1,3 @@
+# Test Coverage
+
+After writing or modifying code, run `sail artisan test --coverage` and ensure 100% coverage is achieved. If coverage is below 100%, add or update tests before finalizing changes.

.ai/rules/index.md

@@ -0,0 +1,4 @@
+# Rules Index
+
+## Coverage
+- `app/**` → coverage.md