17f9d1078f
Root cause: Microsoft Teams Incoming Webhooks require MessageCard JSON
format. The service was sending generic Aegis JSON which Teams rejected
with a 400, incrementing failure_count on every dispatch.
Fix: _send_webhook() now auto-detects the target from the URL:
- webhook.office.com / teams.microsoft.com → Teams MessageCard
(colored card with event title + key/value facts table)
- hooks.slack.com → Slack attachments format
- everything else → current generic Aegis JSON
Also resets failure_count=0 in production so the webhook starts fresh.