chore: bump version to v2026.4.341 and improve AI error handling}
- Bump version from v2026.4.340 to v2026.4.341 in package.json, README.md, and artifacts/cluster.md
- Extract Groq API error codes in ai-redis-query error handler for 403 (blocked_api_access) and 429 (rate_limit) responses
- Return normalized error messages to the client instead of raw exception text