docs: document spec.settings.logger server logging configuration

[arekborucki]

Why

The spec.settings.logger block is fully implemented on both ClickHouseCluster and KeeperCluster (with kubebuilder defaults and an enum-validated level), but it was not documented anywhere in the configuration guide. Users had no reference for how to change the log level, disable file logging, switch to JSON output, ortune log rotation, and no indication that console logging always stays on so kubectl logs keeps working.

What

Adds a Server logging subsection under ClickHouse settings in docs/guides/configuration.mdx:

• Documents all five fields with their defaults: logToFile (true), jsonLogs (false), level (trace; full enum listed), size (1000M), count (50).
• Shows the rendered logger: block so users can see that console logging is always on and file targets (log / errorlog) are only added when logToFile: true`.
• Notes that the same spec.settings.logger block applies to KeeperCluster (files under /var/log/clickhouse-keeper/)

[mintlify]

Docs PR opened: ClickHouse/mintlify-docs-dev#146

Added a Server logging subsection to the Kubernetes operator configuration guide documenting the spec.settings.logger fields and defaults.