Widget Session Init

Resume an identified visitor's most recent session. Creates nothing: a conversation starts with the first `/widget/chat` message, so anonymous and not-yet-known identities get `session_id: null`.

curl -X POST "https://api.getchat9.live/widget/session/init" \
  -H "Content-Type: application/json" \
  -d '{
    "bot_id": "string",
    "user_hints": {},
    "locale": "string"
  }'

{
  "session_id": "1ffd059c-17ea-40a8-8aef-70fd0307db82",
  "mode": "hints",
  "resumed": false
}