feat: add security configuration guidance to AGENTS.md (#580)

Add paragraph to Security & Configuration Tips section explaining
stackql's support for environment variables and command-line arguments
for authentication secrets and configuration, emphasizing integration
with standard deployment practices.

Resolves #579

Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
Co-authored-by: Benevolent General Kroll Who cannot spell <general-kroll-4-life@users.noreply.github.com>

Author: general-kroll-4-life

AGENTS.md

@@ -39,7 +39,7 @@ Please refer to [the developer guide](/docs/developer_guide.md), [the testing su
 
 ## Security & Configuration Tips
 
-- WIP.
+StackQL supports flexible configuration management, including authentication secrets and connection parameters, through environment variables and command-line arguments. This design enables seamless integration with standard deployment mechanisms such as container orchestration platforms, CI/CD pipelines, and configuration management tools, allowing sensitive credentials to be managed securely through established DevOps practices rather than hard-coded in scripts or configuration files.
 
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