Update to Go 1.22+ and refresh all dependencies

[renecannao]

Task 1 of Phase 1

Plan: docs/superpowers/plans/2026-03-23-phase1-foundation-poc.md

What

• Update go.mod from Go 1.18 to Go 1.22
• Remove obsolete //go:build go1.16 constraint from downloads/tarball_registry.go
• Update all direct dependencies to latest stable versions
• Run govulncheck and resolve any vulnerabilities
• Verify compilation and all unit tests pass

Files

• go.mod
• go.sum
• downloads/tarball_registry.go

Acceptance criteria

• go.mod specifies go 1.22
• All direct dependencies updated to latest
• govulncheck ./... reports no critical vulnerabilities in direct deps
• go build -o dbdeployer . succeeds
• ./test/go-unit-tests.sh passes