Each photo card gains a free-text tags input, sent as a raw comma-separated `tags` form field on upload. The server normalizes it (parseTags), so the clients stay dumb — no tag parsing on-device. - Android: PickedItem.tags + setTags; threaded through UploadQueue → UploadWorker → UploadClient's multipart. - Desktop: a tags QLineEdit per PhotoItemWidget; UploadClient.upload sends it.