chore(ci): pin actions and add tools module for CI

[SVilgelm]

Update GitHub Actions workflows to use action SHAs foractions/checkout actions/setup-go, reproducible runner
behavior. Replace direct golangci-lint action usage with explicit linter
commands that run via the project's tools module. Change test reporting
and lint invocations to use go tool -modfile=".github/tools/go.mod" so
they use pinned tool dependencies.

Add .github/tools/go.mod to pin CI tool dependencies (golangci-lint,
go-junit-report, and many lint rules/plugins) and add dependabot config
to keep the tools module up to date weekly. Rename the GolangCI-Lint job
to Lint and split its steps into a config verification and an explicit
run step.

These changes improve CI stability, reproducibility, and dependency
management for tooling.

[Copilot]

Pull Request Overview

This PR improves CI stability and reproducibility by pinning GitHub Actions to specific SHAs and consolidating tool dependencies into a dedicated module. The changes replace version-based action references with immutable SHA references and introduce a tools module to manage CI tool dependencies like golangci-lint and go-junit-report.

• Pin GitHub Actions (checkout, setup-go) to specific commit SHAs for reproducible builds
• Add .github/tools/go.mod module to manage CI tool dependencies with pinned versions
• Replace direct tool installations with go tool -modfile commands for consistent tooling

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated no comments.

File	Description
.github/workflows/release.yaml	Pin actions/checkout and actions/setup-go to commit SHAs
.github/workflows/checks.yaml	Pin actions, replace golangci-lint action with explicit commands, use tools module
.github/tools/go.mod	New tools module defining CI dependencies for golangci-lint and go-junit-report
.github/dependabot.yml	Add dependabot config for tools module with weekly updates

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