chore(release): prepare v2.0.3, simplify release process

[lelia]

Summary

Prepare the v2.0.3 release so customers can receive the latest merged fixes, especially the .NET OpenGrep rule precision improvements from #63.

This also simplifies the release workflow for the current locked-down release environment by removing the automated post-release CHANGELOG.md commit back to main.

Changes

• Bumps Socket Basics from 2.0.2 to 2.0.3
• Updates GitHub Action and Docker docs references to v2.0.3 / 2.0.3
• Syncs derived release metadata in socket_basics/version.py, socket_basics/__init__.py, and action.yml
• Adds entry for v2.0.3 to CHANGELOG.md in this PR (instead of automating as part of release workflow)
• Removes socket-release-bot / direct main push behavior from publish-docker.yml
• Keeps publish automation focused on building, testing, pushing images, and creating the GitHub Release

Testing

• python3 scripts/sync_release_version.py --write
• python3 scripts/sync_release_version.py --check
• uv run --extra dev pytest
• YAML parse validation for edited workflows