fix: grant packages:write permission to Docker publish workflow

GITHUB_TOKEN defaults to read-only for packages. Without packages:write
the push to ghcr.io fails with "installation not allowed to Write organization package".

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Dathan Vance Pattishall

.github/workflows/dockerpublish.yml

@@ -19,6 +19,10 @@ env:
   username: ${{ github.actor }}  # This is your GitHub username automatically
   password: ${{ secrets.GITHUB_TOKEN }} # No setup required!
 
+permissions:
+  contents: read
+  packages: write
+
 jobs:
 
   build_and_publish: