add support for SNI override

[joe-clickhouse]

Summary

Adds support for CLICKHOUSE_SERVER_HOST_NAME environment variable to enable SNI (Server Name Indication) override during TLS connections.

Usage

export CLICKHOUSE_HOST=load-balancer.example.com
export CLICKHOUSE_SERVER_HOST_NAME=server.example.com

Closes #126

[Copilot]

Pull request overview

Adds a configurable SNI/certificate-validation hostname override for ClickHouse TLS connections (via CLICKHOUSE_SERVER_HOST_NAME) to support connecting through load balancers/proxies where the connection endpoint hostname differs from the certificate hostname.

Changes:

• Introduces CLICKHOUSE_SERVER_HOST_NAME to override TLS SNI / hostname validation by passing server_host_name into clickhouse_connect.get_client.
• Updates connection logging to include server_host_name when configured.
• Documents the new environment variable in the README.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
mcp_clickhouse/mcp_server.py	Logs server_host_name when present to make TLS/SNI overrides visible in runtime diagnostics.
mcp_clickhouse/mcp_env.py	Adds CLICKHOUSE_SERVER_HOST_NAME env var support and includes it in the ClickHouse client config dict.
README.md	Documents CLICKHOUSE_SERVER_HOST_NAME usage and behavior.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

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