chore: update go version to 1.26.4

[jingxiang-z]

Description

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

Summary by CodeRabbit

• Chores
  • Upgraded Go toolchain version from 1.26.3 to 1.26.4 across all CI workflows, Docker images, linting configuration, and project dependencies.

[coderabbitai]

📝 Walkthrough

Walkthrough

Go version bumped from 1.26.3 to 1.26.4 across the project's module definition, CI workflows, linter configuration, container images, and development documentation. No functional logic changes; all updates are version string replacements.

Changes

Go Version Bump

Layer / File(s)	Summary
Build system and CI configuration go.mod, .golangci.yml, .github/workflows/ci.yml, .github/workflows/release.yml, Dockerfile, Dockerfile.citests	Go module version directive in go.mod updated to 1.26.4. Golangci-lint run.go version setting updated. CI and release workflow GO_VERSION environment variables updated. Container base images for build and CI testing updated to golang:1.26.4.
Documentation updates CONTRIBUTING.md, docs/development.md	Go version prerequisite documented in contributor and development guides updated to reference 1.26.4 instead of 1.26.3 (and 1.24+ in contributing guide).

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

🐰 A version bump hops into sight,
From point three to point four takes flight,
Through workflows and docs it gently springs,
No logic breaks, just version strings,
The toolchain leaps with rabbit delight! 🎉

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately and concisely describes the main change: updating the Go version to 1.26.4 across all project files.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/update-go-version

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