feat: auto-close sidebar on mobile when navigating to content

- Add effect to close sidebar when route changes on mobile
- Handles clicking on blog posts in Explore view
- Complements existing sidebar auto-close for bookmarks and highlights
- Improves mobile UX by preventing sidebar from blocking content

.cursor/rules/mobile-first-ui-ux.mdc

@@ -0,0 +1,3 @@
+---
+alwaysApply: true
+---

src/components/Bookmarks.tsx

@@ -90,6 +90,14 @@ const Bookmarks: React.FC<BookmarksProps> = ({ relayPool, onLogout }) => {
     setHighlightVisibility
   } = useBookmarksUI({ settings })
 
+  // Close sidebar on mobile when route changes (e.g., clicking on blog posts in Explore)
+  useEffect(() => {
+    if (isMobile && isSidebarOpen) {
+      toggleSidebar()
+    }
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, [location.pathname])
+
   const {
     bookmarks,
     bookmarksLoading,