Convert ulimits from flat strings to structured dicts with name, soft,
and hard fields for better UI experience. Add default_ulimits as a
configurable setting that dynamically renders into daemon.json, giving
two layers of control: global defaults via the daemon and per-container
overrides.
Add ulimits as a configurable advanced setting for every container,
allowing customization through the web UI. Move hardcoded ulimits
from elasticsearch and zeek into defaults.yaml and fix elasticsearch
ulimits that were incorrectly nested under the environment key.
