Add Backend Dockerfile and workflow

.gitea/workflows/feedmee-test-backend-build-docker.yaml

@@ -0,0 +1,33 @@
+name: Build Feedmee Go Backend App
+
+defaults:
+  run:
+    working-directory: ./backend
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Log in to Gitea Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{vars.REGISTRY_URL}}
+          username: ${{vars.ACTOR}}
+          password: ${{secrets.TOKEN}}
+
+      - name: Build Docker image
+        run: |
+          docker build -f Dockerfile -t ${{vars.REGISTRY_URL}}/${{github.repository}}-backend-test:latest .
+
+      - name: Push Docker image
+        run: |
+          docker push ${{vars.REGISTRY_URL}}/${{github.repository}}-backend-test:latest