Auto-logout users when page is closed

- Create LogoutOnUnload component that triggers logout on page close
- Uses beforeunload/unload events with navigator.sendBeacon() for reliability
- Create /api/logout endpoint that clears both admin and customer sessions
- Add LogoutOnUnload to root layout so it runs on all pages
- Works for both admin and customer users

Behavior:
- When user closes browser tab/window, logout happens automatically
- Session cookies are cleared via API endpoint
- Improves security by preventing session hijacking from closed windows

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/components/LogoutOnUnload.tsx

@@ -0,0 +1,27 @@
+'use client';
+
+import { useEffect } from 'react';
+
+/**
+ * Logs out the user when they close/leave the page
+ * Works for both admin and customer sessions
+ */
+export default function LogoutOnUnload() {
+  useEffect(() => {
+    const handleUnload = () => {
+      // Use sendBeacon to reliably send logout even when page is closing
+      // This doesn't wait for a response, which is fine for logout
+      navigator.sendBeacon('/api/logout');
+    };
+
+    window.addEventListener('beforeunload', handleUnload);
+    window.addEventListener('unload', handleUnload);
+
+    return () => {
+      window.removeEventListener('beforeunload', handleUnload);
+      window.removeEventListener('unload', handleUnload);
+    };
+  }, []);
+
+  return null;
+}