perf: Optimize list membership fetching during export

Instead of calling getListsOfBookmark for each bookmark (N calls),
now iterate through lists and get bookmarks for each list (L calls).
This significantly improves performance when L << N, which is the
typical case (e.g., 10 lists vs 1000 bookmarks).

apps/web/app/api/bookmarks/export/route.tsx

@@ -43,23 +43,44 @@ export async function GET(request: NextRequest) {
       ? listsResponse
       : listsResponse.lists;
 
-    // Fetch list memberships for each bookmark
+    // Build a map from bookmark ID to list IDs by querying each list
     const bookmarkListMap = new Map<string, string[]>();
-    for (const bookmark of bookmarks) {
+    for (const list of lists) {
       try {
-        const bookmarkListsResponse = await api.lists.getListsOfBookmark({
-          bookmarkId: bookmark.id,
+        // Get all bookmarks in this list
+        const listBookmarks = await api.bookmarks.getBookmarks({
+          listId: list.id,
+          limit: 1000, // Use a large limit to get all bookmarks
+          includeContent: false, // We don't need the content, just IDs
         });
-        // Handle both array and object with lists property
-        const listArray = Array.isArray(bookmarkListsResponse)
-          ? bookmarkListsResponse
-          : bookmarkListsResponse.lists ?? [];
-        bookmarkListMap.set(
-          bookmark.id,
-          listArray.map((l: { id: string }) => l.id),
-        );
+
+        // Add this list ID to each bookmark's list array
+        for (const bookmark of listBookmarks.bookmarks) {
+          const existingLists = bookmarkListMap.get(bookmark.id) || [];
+          existingLists.push(list.id);
+          bookmarkListMap.set(bookmark.id, existingLists);
+        }
+
+        // Handle pagination if there are more bookmarks
+        let cursor = listBookmarks.nextCursor;
+        while (cursor) {
+          const moreBookmarks = await api.bookmarks.getBookmarks({
+            listId: list.id,
+            cursor,
+            limit: 1000,
+            includeContent: false,
+          });
+
+          for (const bookmark of moreBookmarks.bookmarks) {
+            const existingLists = bookmarkListMap.get(bookmark.id) || [];
+            existingLists.push(list.id);
+            bookmarkListMap.set(bookmark.id, existingLists);
+          }
+
+          cursor = moreBookmarks.nextCursor;
+        }
       } catch {
-        bookmarkListMap.set(bookmark.id, []);
+        // Skip lists that can't be accessed
       }
     }