💄 style : Modify root style in global.css

- Unify the root css background to white
- We don't have plans to offer a dark mode at this time, so this will be a future fix.

Related issue: YJU-OKURA#30

src/app/globals.css

@@ -4,17 +4,17 @@
 
 :root {
   --foreground-rgb: 0, 0, 0;
-  --background-start-rgb: 214, 219, 220;
+  --background-start-rgb: 255, 255, 255;
   --background-end-rgb: 255, 255, 255;
 }
 
-@media (prefers-color-scheme: dark) {
+/* @media (prefers-color-scheme: dark) {
   :root {
     --foreground-rgb: 255, 255, 255;
     --background-start-rgb: 0, 0, 0;
     --background-end-rgb: 0, 0, 0;
   }
-}
+} */
 
 body {
   color: rgb(var(--foreground-rgb));