TikTok accepts a workers.dev URL prefix for PULL_FROM_URL photo hosting

TikTok's developer portal (app top bar, 'URL properties', per sandbox or Production) accepted a URL prefix property on a *.workers.dev subdomain, e.g. https://<worker>.<sub>.workers.dev/p/. Domain properties need a DNS TXT record you can't set on workers.dev, but a URL prefix only needs a signature file (tiktok<random>.txt, contents 'tiktok-developers-site-verification=<random>', 68 bytes, no newline) served as a plain 200 at <prefix><filename>. A small 'Verify' next to the URL field only generates the file; the red Verify in the next dialog checks it. If R2 isn't enabled, a Cloudflare Worker with one SQLite-backed Durable Object per batch (new_sqlite_classes, works on Workers Free) can hold images split into 1 MiB BLOB rows (the row limit is 2 MB), with a DO alarm for expiry. 20 MB PUT and GET round trips stayed within Free-plan CPU. Right after 'wrangler secret put', requests got intermittent 401s for about 20 s while the new version propagated.