라이트 모드 버튼 스타일 수정

frontend/index.html

@@ -1,9 +1,17 @@
 <!doctype html>
-<html lang="ko">
+<html lang="ko" class="theme-dark">
   <head>
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
     <title>BizCare</title>
+    <script>
+      try {
+        var t = localStorage.getItem('bizcare_ui_theme')
+        if (t === 'light' || t === 'dark' || t === 'blue') {
+          document.documentElement.className = 'theme-' + t
+        }
+      } catch (e) {}
+    </script>
   </head>
   <body>
     <div id="root"></div>