fix(kafka): align concurrency limits with syslog

[xiami762]

Summary

• raise the Kafka workflow worker cap from 2 to 8
• raise the Kafka queue cap from 100 to 1000
• align Kafka concurrency limits with the Syslog manager while preserving Kafka backpressure behavior

Root cause

Kafka trigger settings were silently capped below the requested values by lower manager-level safety limits.

Validation

• uv run ruff check flocks/ingest/kafka/manager.py
• uv run pytest -q tests/ingest/test_kafka_manager.py (16 passed)