fix: prevent useAuth infinite loop causing rate limit storms

checkAuth was defined as a plain function and used as a useEffect
dependency, causing it to fire on every render. Moved it inside the
effect with an empty dependency array so it runs once on mount.

apps/web/src/hooks/use-auth.ts

@@ -14,9 +14,6 @@ export function useAuth(): AuthState {
   });
 
   useEffect(() => {
-    checkAuth();
-  }, [checkAuth]);
-
     async function checkAuth() {
       try {
         // Check if auth is enabled
@@ -51,5 +48,8 @@ export function useAuth(): AuthState {
       }
     }
 
+    checkAuth();
+  }, []);
+
   return state;
 }