Enable bodyclose, makezero, and sqlclosecheck linters

[dgageot]

Add three new linters to golangci-lint configuration and fix all reported issues:

• bodyclose: ensure HTTP response bodies are closed in tests; add nolint for false positives (websocket upgrade, goroutine-deferred close)
• makezero: use make+append instead of make+copy in hasCycle
• sqlclosecheck: use defer rows.Close() instead of manual close calls

[docker-agent]

Assessment: 🟢 APPROVE

This PR cleanly enables three new golangci-lint linters and fixes all reported issues:

• ✅ bodyclose: Adds defer resp.Body.Close() in test files, with appropriate //nolint directives for websocket upgrades and goroutine-deferred closes
• ✅ makezero: Optimizes slice initialization in hasCycle function (make+append instead of make+copy)
• ✅ sqlclosecheck: Consolidates manual rows.Close() calls into a single defer rows.Close() statement, properly placed after error checking

All changes are linter-driven improvements with no bugs introduced. The defer rows.Close() placement is correct (after error checks), and the slice optimization is functionally equivalent.