chore(ci): add explicit GITHUB_TOKEN permissions to workflows

[ilhan007]

Summary

Add explicit top-level permissions: blocks to all GitHub Actions workflows to follow the principle of least privilege and prepare for GitHub's upcoming enforcement of read-only default GITHUB_TOKEN permissions.

Permissions Applied

Workflow	Permission	Reason
ci.yml	contents: read	Only checks out code and runs build — no write access needed
lint.yml	contents: read	Only checks out code and runs linting — no write access needed
deploy.yml	contents: write	Uses JamesIves/github-pages-deploy-action which pushes the built artifacts to the gh-pages branch

Context

GitHub is enforcing read-only as the default permission for GITHUB_TOKEN in all new repositories, and will roll this out more broadly. Adding explicit permissions ensures workflows continue to function correctly after this change, and documents the intended access level for each workflow.