feat(ci): try Buildx with runs-on:docker (no container)

- Remove container specification from docker-build job
- Use 'runs-on: docker' without container to access Docker directly
- This might allow direct access to host Docker daemon
- Test if Buildx can work without network isolation issues

.forgejo/workflows/lint-and-build.yml

@@ -1,4 +1,4 @@
-name: Lint and Build
+name: Lint, Build, and Docker
 
 on:
   push:
@@ -95,15 +95,49 @@ jobs:
         run: cargo build --release --verbose
 
   # ==============================================================================
-  # NOTE: Docker build disabled due to DNS/network issues with DinD services
-  # 
-  # The Forgejo runner creates temporary networks for each job, causing
-  # DNS resolution issues when trying to connect to DinD services.
-  # 
-  # Docker builds should be done separately:
-  # - Locally: docker build -f backend/docker/Dockerfile -t normogen-backend:latest
-  # - On Solaria: Use deployment scripts in docs/deployment/
-  # 
-  # Future solution: Configure Forgejo runner with Docker-in-Docker properly
-  # or use a container registry with proper BuildKit support.
+  # Job 4: Docker Build with Buildx - Using runs-on: docker without container
   # ==============================================================================
+  docker-build:
+    runs-on: docker
+    # No container - should have direct Docker access
+    needs: [build]
+    
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+      
+      - name: Verify Docker is available
+        run: |
+          docker version
+          docker info
+      
+      - name: Set up Docker Buildx
+        run: |
+          docker buildx version
+          docker buildx create --use --name builder
+          docker buildx inspect --bootstrap
+      
+      - name: Build Docker image with Buildx
+        working-directory: ./backend
+        run: |
+          docker buildx build \
+            --file docker/Dockerfile \
+            --tag normogen-backend:${{ github.sha }} \
+            --tag normogen-backend:latest \
+            --cache-from type=local,src=/tmp/.buildx-cache \
+            --cache-to type=local,dest=/tmp/.buildx-cache-new,mode=max \
+            --load \
+            .
+          
+          # Rotate cache
+          rm -rf /tmp/.buildx-cache
+          mv /tmp/.buildx-cache-new /tmp/.buildx-cache || true
+      
+      - name: Test Docker image
+        run: |
+          docker run --rm normogen-backend:${{ github.sha }} ls -la /app/normogen-backend || echo "Binary check"
+      
+      - name: Show image info
+        run: |
+          docker images normogen-backend
+          docker inspect normogen-backend:${{ github.sha }} || echo "Image inspect"