When Ollama isn't installed, every ZIM download dispatches embedding jobs
that fail and retry 30x with 60s backoff. With many ZIM files downloading
in parallel, this exhausts Redis connections with EPIPE/ECONNRESET errors.
Two changes:
1. Don't dispatch embedding jobs when Ollama isn't installed (belt)
2. Use BullMQ UnrecoverableError for "not installed" so jobs fail
immediately without retrying (suspenders)
Closes#351
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>