chore: Update Go dependencies to latest versions

Summary

Update all Go dependencies to their latest versions across the root module and pkg/testutil/oci module.

Changes

Root module (go.mod):

• github.com/go-git/go-git/v5: v5.17.0 → v5.17.2
• github.com/klauspost/compress: v1.18.4 → v1.18.5
• github.com/ProtonMail/go-crypto: v1.3.0 → v1.4.1
• golang.org/x/exp: 20260218 → 20260312
• golang.org/x/mod: v0.33.0 → v0.34.0
• golang.org/x/crypto: v0.48.0 → v0.49.0
• golang.org/x/net: v0.50.0 → v0.52.0
• golang.org/x/sys: v0.41.0 → v0.42.0
• golang.org/x/text: v0.34.0 → v0.35.0
• google.golang.org/grpc: v1.79.2 → v1.80.0
• google.golang.org/genproto/googleapis/rpc: 20260217 → 20260406

OCI testutil module (pkg/testutil/oci/go.mod):

• github.com/distribution/distribution/v3: v3.0.0 → v3.1.0
• github.com/docker/go-events: 20190806 → 20250808
• github.com/grpc-ecosystem/grpc-gateway/v2: v2.27.3 → v2.28.0
• github.com/hashicorp/golang-lru/v2: v2.0.5 → v2.0.7
• github.com/klauspost/compress: v1.18.4 → v1.18.5
• github.com/prometheus/common: v0.67.4 → v0.67.5
• github.com/prometheus/procfs: v0.19.2 → v0.20.1
• github.com/redis/go-redis/v9: v9.7.3 → v9.18.0
• OpenTelemetry packages: v1.41.0 → v1.43.0
• google.golang.org/grpc: v1.79.1 → v1.80.0

Pinned dependencies

• github.com/docker/cli remains pinned at v28.x for gitlab-runner compatibility (moby/docker type conflict)

Additional files

• Added .claude/commands/sr-go-update-deps.md with instructions for future dependency updates