chore: Modernize CI pipeline, update dependencies, and fortify build process

[dmirtillo]

Description

Hello! 👋

I've been using rcon-cli and noticed a few areas in the build, distribution, and CI/CD pipeline that could be modernized to improve developer experience, increase build speed, and fortify the security of the released Docker images.

This PR bundles those improvements into a cohesive update that aligns local development with a robust, automated CI pipeline, culminating in a fully automated, multi-platform release process powered by GoReleaser.

🛠 What changed

1. Automated Release Pipeline (GoReleaser)

• Replaced the manual scripts/local/compile.sh bash script with an industry-standard .goreleaser.yaml configuration.
• The CI pipeline now automatically handles cross-compiling binaries (Linux, Windows, macOS across amd64, 386, and arm64), generating tar.gz/zip archives, and computing SHA256 checksums whenever a new v* git tag is pushed.
• Automatically generates and publishes rich GitHub Releases with changelog notes.

2. Fortified Multi-Arch Docker Pipeline & GHCR Migration

• Migrated the Docker image registry target from Docker Hub to GitHub Container Registry (ghcr.io).
• Multi-Arch Support: GoReleaser is configured via dockers_v2 (using docker buildx and QEMU) to natively build and publish multi-arch Docker images (linux/amd64 and linux/arm64).
• Validation Steps: The CI pipeline now explicitly validates the Docker image before pushing:
  • hadolint to statically analyze the Dockerfile.
  • A local verification build (load: true).
  • A runtime smoke test (docker run /rcon --help) to ensure the binary boots correctly in the Alpine runner.
  • A trivy security scan to check for CRITICAL or HIGH vulnerabilities.
• Base Image Security: Updated the Dockerfile base image to Alpine 3.23 and added apk upgrade during the build to automatically patch critical OS-level vulnerabilities (e.g., CVE-2026-22184 in zlib).

3. CI Pipeline Refactoring (GitHub Actions)

• Parallelization: Split the monolithic build job in build.yml into distinct, granular jobs (lint, test, and build). This allows linting and testing to run concurrently, speeding up the feedback loop.
• Fail-Fast Releases: The release job now explicitly needs: [lint, test, build, docker-ci]. Previously, it ran independently, meaning a broken commit could theoretically still trigger a published Docker image.
• Local Alignment: Added deps, test, build, and lint targets to the Makefile so developers can run the exact same checks locally that run in CI. Added a CONTRIBUTING.md guide to document this workflow.

4. Go Toolchain & Dependency Modernization

• Bumped the Go version uniformly to 1.26 across go.mod and .github/workflows/build.yml.
• Upgraded the linter to golangci-lint v2.10.1 and configured the GitHub Action (golangci-lint-action@v9) to use install-mode: go-install to ensure strict compatibility with Go 1.26. Cleaned up deprecated linter rules and fixed discovered issues.
• Added a .github/dependabot.yml configuration to automatically track and update Go modules, GitHub Actions, and Docker base images weekly.

🧪 How it was tested

• All tests pass locally via make test.
• The golangci-lint passes cleanly without warnings via make lint.
• The GitHub Actions pipeline was tested end-to-end via a pre-release tag (v0.11.0). It correctly ran jobs in parallel, validated the Docker image, published the multi-arch images to GHCR, and created the GitHub Release with the cross-compiled binaries.

Let me know if you'd like any adjustments to the approach or if you'd prefer me to split any of these changes into separate PRs. Thank you for the great project!