fix: grant GITHUB_TOKEN contents write permission for release creation

[Rubyj]

Summary of Changes

Adds permissions: contents: write to the release job so the built-in GITHUB_TOKEN can create GitHub Releases and upload zip assets. Without this, the packager fails with a 403 when attempting to publish the release.

Testing

After merging, delete and re-push the v1.2.0 tag to re-trigger the release workflow:

git tag -d v1.2.0
git push origin --delete v1.2.0
git tag -a v1.2.0 -m "Version 1.2.0"
git push origin v1.2.0

Checklist

• Tested in-game on Midnight (Interface 120001)
• No new global variables introduced (or .luacheckrc updated if needed)
• No taint-unsafe patterns introduced (no runtime CreateFrame, SetParent, or SetScript on secure frames)
• Data.lua spell entries include both duration and defaultDuration
• New dev-only files added to .pkgmeta ignore list
• ## Version: in CooldownTracker.toc bumped if this is a release