fix: disable self-observe by default, fix crash causes

- ENABLE_SELF_OBSERVE env var (default false) gates self-observe
- Fix UA condition: empty UA no longer triggers logging
- Add per-IP dedup (5min) to prevent 1M+ row storms
- Remove _cache=null from selfObserve (was busting cache on every hit)
- Add 90-day row pruning on startup + every 6h
- Add enrichCache TTL cleanup every 5min to prevent unbounded memory growth

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose.yml

@@ -12,6 +12,7 @@ services:
       - DB_PATH=/data/bots.db
       - NODE_ENV=production
       - API_TOKEN=${API_TOKEN:-change-me-to-a-long-random-string}
+      - ENABLE_SELF_OBSERVE=false
     healthcheck:
       test: ["CMD", "wget", "-qO-", "http://localhost:3091/api/v1/health"]
       interval: 30s