stickers-from-roblox worker.
Usage: /pack/<userId>/<packName>
  + /pack.json /sheet.pdf?template=... /ios.zip /raw.zip /sticker/<mood>.png
Listing:    /packs/recent?limit=N&cursor=C
Thumbnails: /thumb/user/<userId>?size=420x420 /thumb/asset/<assetId>?size=420x420
OAuth:      POST /oauth/token  (PKCE code/refresh -> tokens; iOS calls this)
            GET  /me           (Bearer token; identity sanity check)
            GET  /me/packs    (Bearer token; caller's pack list)
Privacy/Terms: https://www.bitwiseandrea.com/projects/{privacy,terms}