chore: Upgrade Go toolchain to 1.26

[behzad-mir]

Summary

Upgrade the Go toolchain from 1.24 to 1.26 across the ACN repository.

Prerequisites

• chore: FIPS-ready base image migration (distroless/minimal → distroless/base) #4364 (FIPS-ready base image migration) must be merged first

Motivation

• Go 1.26 enforces FIPS-compliant system crypto
• Security patches and performance improvements
• Ecosystem compatibility

Files to Update

Template-managed (auto via make dockerfiles)

• build/images.mk GO_IMG: 1.24-azurelinux3.0 → 1.26-azurelinux3.0
• Regenerate all Dockerfiles: make dockerfiles

Manual updates

• go.mod: go 1.24.1 → go 1.26 + go mod tidy
• .pipelines/build/scripts/install-go.sh: update DEFAULT_IMAGE SHA
• bpf-prog/ipv6-hp-bpf/linux.Dockerfile: update to Go 1.26 MCR SHA
• npm/linux.Dockerfile: update tag to 1.26.x
• npm/windows.Dockerfile: update tag to 1.26.x
• .devcontainer/Dockerfile: VARIANT="1.24" → "1.26"

SHA Lookup Commands

# azurelinux3.0
skopeo inspect docker://mcr.microsoft.com/oss/go/microsoft/golang:1.26-azurelinux3.0 --format "{{.Digest}}"

# MCR Go (for bpf-prog)
skopeo inspect docker://mcr.microsoft.com/oss/go/microsoft/golang:1.26 --format "{{.Digest}}"

Verification

• docker run --rm <image>@<sha> go version confirms Go 1.26
• Pipeline passes — check "Install msft-go" logs for correct SHA
• go mod tidy completes without errors
• ARM and AMD builds both succeed

[github-actions]

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