API v1: campaigns, leads, mailboxes, and the inbox

The public API now covers everything the app does. Alongside find-email, find-mobile, verify-email, and reverse-email-lookup, /v1 exposes campaigns and their sequences, lead upsert and batch import, email account settings, pause, resume, and disconnect, and the inbox with message forwarding.

Access keys are created under Account, revealed once, and stored only as a hash. Limits apply per key and per route, with rate-limit headers on every response.