ci(docker): add Docker publishing workflow and Dockerfile

Introduce GitHub Actions workflow for automated Docker image
publishing to Docker Hub, along with a dedicated Dockerfile in
the ci directory to streamline container builds.

.github/workflows/docker-publish.yml

@@ -2,7 +2,7 @@ name: Publish Docker image
 
 on:
   push:
-    branches: [master, ci/docker-hub-publishing]
+    branches: [master]
   release:
     types: [published]
 
@@ -24,19 +24,18 @@ jobs:
 
       - name: Extract metadata (tags, labels) for Docker
         id: meta
-        uses: docker/metadata-action@9ec57ed1fcdbf14dcef7dfbe97b2010124a938b7
+        uses: docker/metadata-action@c299e40c65443455700f0fdfc63efafe5b349051
         with:
           images: cproofdev/cproof
           tags: |
             type=raw,value=dev,enable={{is_default_branch}}
-            type=raw,value=test,enable={{is_not_default_branch}}
             type=sha,prefix=nightly-,enable={{is_default_branch}}
             type=ref,event=tag
             type=raw,value=latest,enable=${{ startsWith(github.ref, 'refs/tags/') }}
 
       - name: Build and push Docker image
         id: push
-        uses: docker/build-push-action@3b5e8027fcad23fda98b2e3ac259d8d67585f671
+        uses: docker/build-push-action@2bd26e71295ee32cbf6a73510d165bf7232460f3
         with:
           context: .
           file: ./ci/Dockerfile