ci: fetch tags for landing version deploys

[jb-thery]

Summary

• fetch full history and tags in the landing deploy workflow so git describe can resolve the latest released version
• prevents later landing-only deploys from dropping Ragmir v2.4.0 from the live page

Validation

• git diff --check
• pnpm lint
• local YAML parse for .github/workflows/deploy-landing.yml
• GitNexus detect-changes --repo jcode-ragmir returned no indexed symbol changes

Docs

• actions/checkout docs say fetch-depth: 0 fetches all history for all branches and tags