App Chat spike (test contacts only)

Customer sends (inbound) Chat ID
Optional contact fields: firstName phone (E.164, your own)
Customer uploads a real file (inbound file flow) link lives sec
Needs the public URL below so respond.io can fetch it. File is served at a link that dies after the TTL.
Public (ngrok) URL — paste your https ngrok address
How /message answers respond.io slow seconds