Honestly, since the first day I switched to Firefox I'm just saving to it's own bookmarks. Whenever I wanna check those websites I just open it either from my desktop or my laptop(s), since it's syncing in between my devices.
I don't know if there's much people using bookmarking tools, but to help you see another perspective, as a person who finds bookmarking tools not necessary I'd say it wouldn't worth your time to vibe code one. Also just for "vibe coding", be really really careful if you're gonna make it a "product" because you'll definitely face rough situations through it.
It looks pretty nice, good job!
The bookmarks feature is nice actually, but since I have almost a thousand of them saved in my browser, the page tries to load all of them and I couldn't find anything to remove it only from the new tab page.
I'd strongly suggest you to add a simple feature of custom bookmarks, separated from browser bookmarks.
This is off-topic but, I really don't get why some of those websites are blocked for some countries. For example I'm trying to reach from Türkiye but it seems they blocked the access through here.