fix: make sure fetch function doesn't get called repeatedly on onMount (#4669)

packages/better-auth/src/client/query.ts

@@ -118,13 +118,16 @@ export const useAuthQuery = <T>(
 				fn();
 			} else {
 				onMount(value, () => {
-					setTimeout(() => {
-						fn();
+					const timeoutId = setTimeout(() => {
+						if (!isMounted) {
+							fn();
+							isMounted = true;
+						}
 					}, 0);
-					isMounted = true;
 					return () => {
 						value.off();
 						initAtom.off();
+						clearTimeout(timeoutId);
 					};
 				});
 			}