Add CI pipeline for shell and YAML validation using GitHub Actions

[iamdevdhanush]

Currently, the repository does not have any automated CI checks. This makes it easy for
broken shell scripts or invalid YAML files to be merged without detection.

Introducing a basic CI pipeline will improve reliability, enforce best practices,
and align the repository with standard DevOps workflows.

Proposed Solution

• Add a GitHub Actions workflow triggered on push and pull requests to main
• Use ShellCheck to lint all .sh files
• Use yamllint to validate YAML files
• Fail the workflow if any linting errors are detected

Acceptance Criteria

• CI workflow runs on every push and pull request to main
• Shell scripts are validated using ShellCheck
• YAML files are validated using yamllint
• Workflow fails on linting errors