feat: add initial state management for Sidebar from cookie

src/components/ui/sidebar.tsx

@@ -69,9 +69,25 @@ function SidebarProvider({
   const isMobile = useIsMobile()
   const [openMobile, setOpenMobile] = React.useState(false)
 
+  // Read initial state from cookie
+  const getInitialState = React.useCallback(() => {
+    if (typeof window === "undefined") return defaultOpen
+    
+    const cookie = document.cookie
+      .split("; ")
+      .find((row) => row.startsWith(`${SIDEBAR_COOKIE_NAME}=`))
+    
+    if (cookie) {
+      const value = cookie.split("=")[1]
+      return value === "true"
+    }
+    
+    return defaultOpen
+  }, [defaultOpen])
+
   // This is the internal state of the sidebar.
   // We use openProp and setOpenProp for control from outside the component.
-  const [_open, _setOpen] = React.useState(defaultOpen)
+  const [_open, _setOpen] = React.useState(getInitialState)
   const open = openProp ?? _open
   const setOpen = React.useCallback(
     (value: boolean | ((value: boolean) => boolean)) => {