feat(optimizations): adds memoization for performance optimization

Add currentUserName to video API responses and session for display in comments. Also adds memoization for performance optimization and implements Page Visibility API to pause comment polling when tab is hidden.

app/api/watch/[videoId]/route.ts

@@ -76,6 +76,7 @@ export async function GET(request: NextRequest, { params }: RouteParams) {
             },
             isAuthenticated: !!session?.user?.id,
             currentUserId: session?.user?.id || null,
+            currentUserName: session?.user?.name || null,
             canComment: access.hasAccess,
         });