Outbound usage webhooks + clearer usage limits
- Outbound usage webhooks shipped: register a signed HTTPS endpoint (HMAC-SHA256 via the X-Predax-Signature header) and get notified the moment you cross 80%, 90%, or 100% of your daily or monthly quota — no more polling the dashboard. Manage them under Dashboard → API Settings.
- Usage meters on the dashboard now show both daily and monthly consumption with colour-escalating progress bars and an upgrade prompt as you approach your cap.
- Daily usage warning emails — previously only monthly thresholds were emailed; lower tiers that hit the daily wall first now get an 80% / 90% / 100% heads-up too.
- Rate-limit and quota errors (402 / 413 / 429) now tell you exactly which limit you hit and which plan lifts it, with an upgrade link in the response headers.
