build(*): Improve build automation

.github/workflows/docker.yml

@@ -1,14 +1,9 @@
-name: Docker
+name: Docker CI
 
 on:
   pull_request:
     branches:
       - main
-  push:
-    branches:
-      - main
-    tags:
-      - "v*.*.*"
 
 env:
   IMAGE_NAME: jcreek23/open-network-diagram
@@ -26,30 +21,21 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
-      - name: Log in to Docker Hub
-        if: github.event_name == 'push'
-        uses: docker/login-action@v3
-        with:
-          username: ${{ secrets.DOCKERHUB_USERNAME }}
-          password: ${{ secrets.DOCKERHUB_TOKEN }}
-
       - name: Extract Docker metadata
         id: meta
         uses: docker/metadata-action@v5
         with:
           images: docker.io/${{ env.IMAGE_NAME }}
           tags: |
-            type=raw,value=latest,enable={{is_default_branch}}
+            type=ref,event=pr
             type=sha,prefix=sha-
-            type=semver,pattern={{version}}
-            type=semver,pattern={{major}}.{{minor}}
 
-      - name: Build (PR) / Build+Push (push)
+      - name: Build (PR validation only)
         uses: docker/build-push-action@v6
         with:
           context: .
           file: Dockerfile
-          push: ${{ github.event_name == 'push' }}
+          push: false
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           cache-from: type=gha