feat: add light/dark display switch mode

frontend/src/store/themeStore.ts

@@ -0,0 +1,38 @@
+import { create } from 'zustand';
+import { persist } from 'zustand/middleware';
+
+type Theme = 'light' | 'dark';
+
+interface ThemeState {
+  theme: Theme;
+  toggleTheme: () => void;
+  setTheme: (theme: Theme) => void;
+}
+
+export const useThemeStore = create<ThemeState>()(
+  persist(
+    (set) => ({
+      theme: 'light',
+      toggleTheme: () => set((state) => {
+        const newTheme = state.theme === 'light' ? 'dark' : 'light';
+        if (newTheme === 'dark') {
+          document.documentElement.classList.add('dark');
+        } else {
+          document.documentElement.classList.remove('dark');
+        }
+        return { theme: newTheme };
+      }),
+      setTheme: (theme: Theme) => set(() => {
+        if (theme === 'dark') {
+          document.documentElement.classList.add('dark');
+        } else {
+          document.documentElement.classList.remove('dark');
+        }
+        return { theme };
+      }),
+    }),
+    {
+      name: 'theme-storage',
+    }
+  )
+);