Add HikariCP connection pool to SqlServer

[Ma77Ball]

Task Summary

Summary

SqlServer.scala currently opens a fresh PostgreSQL connection (TCP + SCRAM-SHA-256 auth) on every query. Add a HikariCP connection pool so queries reuse pre-authenticated connections instead.

Tasks

• Add HikariCP dependency if not already present
• Replace direct DSL.using(...) setup in SqlServer.scala with a HikariDataSource-backed DSLContext
• Configure pool defaults (max size, min idle, timeouts)
• Add close() and update clearInstance() to call it so tests don't leak pool threads
• Verify existing tests pass

Acceptance Criteria

• All queries go through the pool
• Public API of SqlServer is unchanged
• Existing tests pass

Task Type

• Refactor / Cleanup
• DevOps / Deployment / CI
• Testing / QA
• Documentation
• Performance
• Other

[Ma77Ball]

/take