chore(deps): bump grpc 1.83.1 and x/crypto 0.56.0 to clear govulncheck

[mayankpande88]

Description

The vuln CI job fails on every open PR (#153–#157) because of:

• GO-2026-6348, in grpc 1.83.0 (fixed in 1.83.1);
• GO-2026-6354 and GO-2026-6355, in x/crypto 0.55.0 (fixed in 0.56.0).

x/crypto 0.56.0 requires Go 1.26, so the go directive moves from 1.25.13 to 1.26.6. That matches the Dockerfile build image (golang:1.26.6). Pinning 1.26.0 would make CI (go-version-file: go.mod) install a toolchain with stdlib vulnerabilities that were fixed in later 1.26 patches.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Enhancement (non-breaking change which improves existing functionality)
• Refactor (non-breaking change which improves code structure)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation
• CI/CD

How Has This Been Tested?

• Unit tests
• Manual testing

Under go1.26.6, go test ./... passes, govulncheck ./... exits 0, and golangci-lint reports 0 issues.

Checklist

• CLA signed (the CLA bot will prompt on your first PR)
• make validate passes (fmt + lint + test)
• Docs updated if the wire shape, config surface, or proxy module behavior changed

[gemini-code-assist]

Code Review

This pull request updates the Go runtime version to 1.26.6 and upgrades the dependencies golang.org/x/crypto to v0.56.0 and google.golang.org/grpc to v1.83.1. I have no feedback to provide on these changes.