chore: update Docker Hub namespace and improve credential validation

Author: nickytonline

.github/workflows/docker.yml

@@ -9,6 +9,7 @@ on:
 env:
   REGISTRY: docker.io
   IMAGE_NAME: dev-to-mcp
+  DOCKERHUB_NAMESPACE: nickytonline
 
 jobs:
   build:
@@ -43,12 +44,9 @@ jobs:
 
       - name: Validate Docker Hub secrets
         run: |
-          echo "username length: ${#DOCKERHUB_USERNAME}"
-          echo "token length: ${#DOCKERHUB_TOKEN}"
-          if [ -z "$DOCKERHUB_USERNAME" ] || [ -z "$DOCKERHUB_TOKEN" ]; then
-            echo "Missing Docker credentials"
-            exit 1
-          fi
+          set -euo pipefail
+          : "${DOCKERHUB_USERNAME:?Missing Docker credentials}"
+          : "${DOCKERHUB_TOKEN:?Missing Docker credentials}"
         env:
           DOCKERHUB_USERNAME: ${{ secrets.DOCKERHUB_USERNAME }}
           DOCKERHUB_TOKEN: ${{ secrets.DOCKERHUB_TOKEN }}
@@ -67,16 +65,17 @@ jobs:
           file: Dockerfile
           push: true
           tags: |
-            ${{ env.REGISTRY }}/${{ secrets.DOCKERHUB_USERNAME }}/${{ env.IMAGE_NAME }}:latest
-            ${{ env.REGISTRY }}/${{ secrets.DOCKERHUB_USERNAME }}/${{ env.IMAGE_NAME }}:${{ github.sha }}
+            ${{ env.REGISTRY }}/${{ env.DOCKERHUB_NAMESPACE }}/${{ env.IMAGE_NAME }}:latest
+            ${{ env.REGISTRY }}/${{ env.DOCKERHUB_NAMESPACE }}/${{ env.IMAGE_NAME }}:${{ github.sha }}
           cache-from: type=gha
           cache-to: type=gha,mode=max
 
       - name: Update Docker Hub description + short desc
+        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
         uses: peter-evans/dockerhub-description@v3
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
-          repository: ${{ secrets.DOCKERHUB_USERNAME }}/${{ env.IMAGE_NAME }}
+          repository: ${{ env.DOCKERHUB_NAMESPACE }}/${{ env.IMAGE_NAME }}
           readme-filepath: ./README.md
-          short-description: ${{ github.event.repository.description || '' }}
+          short-description: MCP server for the dev.to API (no auth).