Send error details to ADMIN_CHAT_ID (optional secret) whenever the
statuspage webhook handler hits an error path. Uses waitUntil() so
the notification never blocks the 200 response.
- Hash inputs in timingSafeEqual to prevent length leak side-channel
- Add quote escaping to escapeHtml for defense in depth
- Normalize chatId to Number in parseKvKey for type consistency
- Log Retry-After header on 429 rate limit responses
- Slim README to focused overview, move details to docs/
- Add docs/: system-architecture, setup-guide, feature-decisions
- Add documentation section and README guidelines to CLAUDE.md
