fix: resolve login persistence bug and aggressive logout on network blips

- Updated Login.tsx to automatically redirect users to the dashboard if a valid token is already present in localStorage.

- Refactored getUserById to properly throw server/network errors instead of silently returning undefined.

- Updated AuthGuard in App.tsx to gracefully handle network errors without destroying the user's valid localStorage tokens.

App.tsx

@@ -35,15 +35,27 @@ const AuthGuard: React.FC<{ children: React.ReactNode, roles?: string[] }> = ({
 
       try {
         const fetchedUser = await getUserById(storedUserId);
-        if (fetchedUser && fetchedUser.status === 'active') {
-          setUser(fetchedUser);
+        if (fetchedUser) {
+          if (fetchedUser.status === 'active') {
+            setUser(fetchedUser);
+          } else {
+            // User explicitly marked inactive or deleted
+            logout();
+            setUser(null);
+          }
         } else {
+          // If fetchedUser is undefined but didn't throw, it usually means a 401/403/404 (invalid token or user missing).
+          // However, to be safe against random failures, we should only clear if we are sure it's invalid.
+          // For now, if the token is completely rejected, we log out.
           logout();
           setUser(null);
         }
       } catch (err) {
-        console.error("Auth check failed", err);
-        logout();
+        console.error("Auth check failed (network/server error):", err);
+        // DO NOT logout() here. If the server is offline or restarting, 
+        // we shouldn't wipe the user's local storage tokens.
+        // We just leave the user as null, which will redirect them to login,
+        // but their tokens remain so they can auto-login when the server is back.
         setUser(null);
       } finally {
         setLoading(false);
@@ -53,7 +65,7 @@ const AuthGuard: React.FC<{ children: React.ReactNode, roles?: string[] }> = ({
   }, [location.pathname]);
 
   if (loading) {
-    return <div className="flex h-screen items-center justify-center bg-slate-50 text-slate-400">Carregando...</div>;
+    return <div className="flex h-screen items-center justify-center bg-zinc-50 dark:bg-zinc-950 text-zinc-400">Carregando...</div>;
   }
 
   if (!user) {