make login form use dark/light theme

src/components/LoginFormBox.tsx

@@ -8,7 +8,7 @@ const LoginFormBox = styled(Box)(({ theme }) => ({
     alignItems: "center",
     justifyContent: "flex-start",
     background: "url(./images/floating-cogs.svg)",
-  backgroundColor: "#f9f9f9",
+    backgroundColor: theme.palette.mode === 'dark' ? theme.palette.background.default : theme.palette.background.paper,
     backgroundRepeat: "no-repeat",
     backgroundSize: "cover",
 
@@ -53,6 +53,7 @@ const LoginFormBox = styled(Box)(({ theme }) => ({
       marginBottom: "1rem",
       marginLeft: "0.5rem",
     },
-}));
+  }
+));
 
 export default LoginFormBox;