fix: reuse one database pool per Database

[prasadlohakpure]

Summary

• Sessions were calling sql.Open and Close on every database call, so each session owned its own pool and Postgres ran out of connections (janitor.worker.error.new_session).
• One *sql.DB is now opened per Database and reused. Session close only rolls back an uncommitted transaction.
• Queries run on the session transaction when one is open, so FOR UPDATE locks stay held until commit. Pool size comes from max_open_conns and max_idle_conns (defaults 25 and 10).

Testing

1. Before testing started

2. When trying to bombard with 10 concurrent requests, the idle connection never grew beyond 10 (as per maxIdleConn config)

Test plan

• go test ./internal/pkg/database/
• Deploy with database.max_open_conns and database.max_idle_conns set, and confirm janitor new_session errors stop
• Confirm async job claim and janitor stale-job cleanup still commit (status updates and active_jobs deletes)
• Confirm cancel and command/cluster status updates still report rows affected

[wiz-55ccc8b716]

Wiz Scan Summary

Scanner	Findings
Vulnerabilities	-
Sensitive Data	-
Secrets	1
IaC Misconfigurations	-
SAST Findings	-
Software Management Findings	-
Total	1

View scan details in Wiz

To detect these findings earlier in the dev lifecycle, try the Wiz Code extension for VS Code, JetBrains, or Visual Studio.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[prasadlohakpure]

Wiz check is failing due to changes in config file which has test creds. This check is false positive and can be ignored.