chore: update CI workflow and release process

- Replaced `@semantic-release/git` with `@semantic-release/exec` for handling release commands.
- Updated `.releaserc.json` to reflect changes in release command execution.
- Modified CI workflow to streamline the release process, including tagging and Docker image publishing.
- Removed obsolete publish workflow and integrated its functionality into the main CI workflow.
- Enhanced documentation to clarify the new release process and CI pipeline structure.

.gitignore

@@ -4,6 +4,10 @@ node_modules/
 # Generated by deploy/docker/write-bake-override.sh (CI/local bake)
 deploy/docker/docker-bake.override.hcl
 
+# CI-only markers (not committed)
+.release-version
+CHANGELOG.md
+
 # OS
 .DS_Store
 Thumbs.db