Are Snaptide albums public in any way? Could someone stumble onto my client's wedding photos?

No — and this is the heart of the platform. Albums are private, unindexed, and never exposed publicly. They don't appear in search engines, there's no public browsing gallery, and the only ways in are the private guest link, the full-access link (which has a secret token), or scanning the album's QR code. Even then, guests only see their own matched photos. The architecture assumes privacy by default; there's no "make it public" switch you have to remember to leave off.